I've never seen mainline FAs put their personal bags over row 1. I have seen pilots do it, though. There are some united equipment bags (blankets, inflight kit) that usually get put in those bins by the cleaners (occasionally right before/during the boarding process).

The tiny bins over row 1 on a 737 will not fit a roller unless it's exactly the max dimensions for a carry on (and most people's are oversized). If you do manage to fit one roller on each side, where do the other two passengers put their rollers? Not to mention personal items. On a 739 at the Y bulkhead, there's a raft on a/c right and a lav and emergency equipment on a/c left, leaving even less room.

It's definitely a problem, but I can't think of a solution that works across the fleet. Placards don't work - You wouldn't believe the amount of times I've seen people storing stuff in front/on top of emergency equipment.