My roommate wrote me checks for rent I cashed them they bounced now the store is sueing me is this legal

What was store policy at the time? Also since it was your friend then they should have written you the check and then when it bounced you're the one on the hook. From the sounds of it your friend knew what they were doing and from the stores point of view you were in on it. Its actually illegal in most states.

You're lucky the store is suing you and not having you arrested.

I'm assuming the checks were made out to you and you endorsed them over to the store. In that case the responsibility is yours. You can turn around and sue your friend.

Store sues you, you can go after the friend in court