When I'm working (painting), I have my room door closed, my air contioner on. After I make sure the floor is clean & free from dangerous things, I put my hamster cages on the floor & I let my hamsters roam free in my room, one hamster at a time, else they'll kill each other.
I keep the cage doors half open so that the hamsters can go back to their cages anytime to do their business. I once put their food container in front of the door as a kind of stair but they prefer climbing the cage to using the stair.
I don't use the hamster balls anymore now because the balls often got stuck under my drawing table & also because I have to return the hamsters every 30 minutes to their cages so that they won't pee inside the balls.