Actually the bins on the 757 -5500 or 5600 are exact the same. I been working in the cabin of those planes as a flight attendant for about 10 years. The bins on the 757-300's are a new design and can accomadate just about any bag.
On the 757-200's most bags will fit just fine. Just don't stuff the outer front pockets of your rollerboard or have one thats "expandable" and you will be ok. There are a few places the crew can accomadate extra big bags.