Did Churchill and Roosevelt know about the Molotov-Ribbentrop Pact, or the following secret pacts between Nazi Germany and the Soviet Union?

Taylor writes in The Origins of the Second World War that the Pact was a total surprise for Britain . PP 257 and 292

Winston Churchill speech of October 1, 1939 (it is even on youtube):

What is the second event of this first month? It is, of course, the assertion of the power of Russia. Russia has pursued a cold policy of self-interest. We could have wished that the Russian Armies should be standing on their present line as the friends and allies of Poland, instead of as invaders. But that the Russian Armies should stand on this line was clearly necessary for the safety of Russia against the Nazi menace.

At any rate the line is there, and an Eastern Front has been created which Nazi Germany does not dare assail. When Herr von Ribbentrop [German Foreign Minister] was summoned to Moscow last week, it was to learn the fact, and to accept the fact, that the Nazi designs upon the Baltic states and upon the Ukraine must come to a dead stop.

I cannot forecast to you the action of Russia. It is a middle wrapped in mystery inside an enigma; but perhaps there is a key. That key is Russian national interest. It cannot be in accordance with the interest or safety of Russia that Germany should plant itself upon the shores of the Black Sea, or that it should overrun the Balkan states and subjugate the Slavonic peoples of Southeastern Europe. That would be contrary to the historic life interests of Russia.

But here these interests of Russia fall into the same channel as the interests of Britain and France. None of these three powers can afford to see Rumania, Yugoslavia, Bulgaria, and above all Turkey, put under the German heel.

Through the fog of confusion and uncertainty we may discern quite plainly the community of interests which exists between England, France and Russia to prevent the Nazis from carrying the flames of war into the Balkans and Turkey. Thus, at some risk of being proved wrong by events, I will proclaim tonight my conviction that the second great fact of the first month of the war is that Hitler, and all that Hitler stands for, have been and are being warned off the East and Southeast of Europe.

In regards to the French government, they had been informed well in advance by their ambassador in Berlin. The following is extracted directly from the French Yellow Book (my emphasis), a compendium of French diplomatic documents from 1938-1939:

No. 123

M. COULONDRE, French Ambassador in Berlin,
to M. GEORGES BONNET, Minister for Foreign Affairs.
Berlin, May 7, 1939.

I TAKE the liberty of drawing the especial attention of Your Excellency to the information contained in the enclosed report, our informant being in a particularly good position to know the intentions of the Führer and of his principal lieutenants. His new declarations may be summed up as follows:
(1) M. Beck's speech will in no way alter the situation. The Führer is determined to secure the return of Danzig to Germany, as well as the reunion of East Prussia to the Reich.
(2) The Führer is patient and cautious, and will not tackle the question in a direct way, for he knows that in future France and Britain would not give way, and that the coalition which he would have to confront would be too strong. He will go on manoeuvring until his time comes.
(3) The Führer will come to an understanding to this effect with Russia. The day will come when he attains his aims by these means, without the Allies "having any reason, or even any intention, to intervene." It may be that we shall witness a fourth partition of Poland. In any case, "we shall soon see that something is brewing in the East."
(4) The equivocal attitude of Japan has contributed to Herr Hitler's orientation towards the U.S.S.R.
(5) When the Polish question has once been settled, and Germany's military supremacy definitely assured, Germany will be in a position to come to a conference.
...
In my opinion, he may hope to draw advantage from it in three different ways:
(1) By arriving at a more or less tacit agreement with the U.S.S.R. which would assure him of the benevolent neutrality of that country in the event of a conflict, perhaps even of her complicity in a partition of Poland.
(2) By bringing, through the mere threat of a better understanding with the U.S.S.R., pressure simultaneously to bear on Japan and on Poland, in order to induce the former to sign a military alliance, and the latter to agree to the concessions he is asking for.
(3) By bringing the Western Powers, under the threat of collusion between Germany and Russia, to accept certain Soviet demands to which Poland and Rumania would be opposed, and thus to sow discord among the Allies.

And, In The Gathering Storm Churchill writes (in Chapter 20, The Soviet Enigma):

From the moment when Molotov became Foreign Commissar, he pursued a policy of an arrangement with Germany at the expense of Poland. It was not very long before the French became aware of this. There is a remarkable dispatch by the French Ambassador in Berlin, dated May 7 [1939], published in the French Yellow Book, which states that on his secret information he was sure that a Fourth Partition of Poland was to be the basis of the German-Russian rapprochement.

Churchill goes on in that chapter with extensive quotations from Parliament's debate on May 19 [1939] directly addressing the need to form a binding mutual-defense pact with the Soviet Union before Germany did, in order to secure British and French interests in Eastern Europe, in regards to both Poland and Rumania. Both his own and Lloyd George's words are featured prominently.

To conclude the chapter, Churchill notes that, following Molotov's speech on May 19th in rebuttal to Chamberlain's speech in the House of Commons earlier that day:

.... All four countries [Finland, Estonia, Latvia, Lithuania] now refused [an offer of mutual defense and support from the Soviet Union against German aggression], and perhaps in their terror would for a long time have refused, such a condition [the Soviet demand for a guarantee from all its Eastern European neighbours]. Finland and Estonia even asserted that they would consider such a guarantee extended to them without their consent as an act of aggression. On that same day, May 31, Estonia and Latvia signed non-aggression pacts with Germany. ....

It seems clear that al parties concerned, even the victims, were aware of Russian intentions - any that accepted Hitler's bond need merely have noted the value of that bond to Czechoslovakia for an assessment of its worth.

The secret protocol was known to the US government as early as 24 August 1939. It was passed to US diplomat Charles Bohlen by Hans von Herwath, a German diplomat. The US ambassador in Moscow Laurence Steinhardt passed that information to US Secretary of State Cordell Hull on the same day. Hull immediately informed British Secretary of State for Foreign Affairs Edward Halifax, who in turn informed the French. But the French had already learned about the secret protocol from another source on 25 August 1939 through the contacts of their embassy in Berlin. There is also evidence that the news was immediately known to the Italians, Estonians and Latvians.

The Poles didn't know about the secret protocol and so they didn't expect the Soviet invasion of 17 September 1939. The fact that the British didn't pass that information to their Polish allies is a direct betrayal of Article 5 of the British-Polish alliance agreement from 25 August 1939:

Contracting Parties ... will exchange complete and speedy information concerning any development which might threaten their independence and, in particular, concerning any development which threatened to call the said undertakings into operation.

Sources: the memories of US diplomat Charles Bohlen, the correspondence of the US embassy in Moscow, the memories of Hans von Herwath, "German-Soviet relations 1939-1941" by Slawomir Debski.