Upvote:0
You may use your temporary residence permit (see https://www.mae.ro/en/node/2040), but you risk to misuse it. The residence permit probably come with some obligation. For sure it doesn't allow you to use it to reside elsewhere in EU, but it allow you to travel in Romania.
So, you should be able to enter into Romania (under some conditions) and stay there (also with some conditions) but not more than the validity of the Polish permit. You should carefully check not to have more troubles (and a ban) (either in Poland or in Romania). You may need to read carefully the linked site and relative documents, there are many rules so you should check what apply to you.
Personally, I would have some doubt about you want to study in Romania, but you do no understand the local language. I think this could raise questions for your study permit.