Free roaming is an amazing way to let your hamster get exercise, and is a method I have used with all my Syrians. They've all loved it to a certain degree at least and it's super fun to watch them run all about. I however wouldn't recommend the bathroom just because of how many cleaners there are, bits of bacteria and nasty stuff, and too many opportunities to squeeze in and behind things. Even if you think your bathroom is safe, your hamster may surprise you. I once lost one of my gerbils underneath my sink because there was a minuscule crevice she squeezed into. I had checked everything over twice and thought I'd seen everything, but things sometimes slip by and bathrooms all tend to have these tiny spaces behind toilets, under cabinets, and under sinks. A carpeted bedroom or some other non-restroom type area would probably make a better place to roam. Make sure to leave out tunnels, boxes, and other hideouts so they feel comfortable. I also would only allow a Syrian to free roam as a dwarf- say like a robo, would be gone in seconds! Free roaming, when done right, is extremely beneficial