Upvote:4
Ultimately, your roll-a-board is too big by Amtrak rules. It really doesn't matter how much too big, it violates the rule.
So your decision is really do you risk it or not. Just because some folks have experienced lax inspections of baggage size, doesn't mean all employees are lax with their judgement nor does it mean the rules won't apply. Even if 90% of travelers get away with it, what happens if you are amongst that 10% that don't?
Do you have a plan B in case they do determine that your bag is too big? Do you have a smaller suitcase that you can use and be safe?