Sent to Collection agency because roommate failed to pay damages done to apartment?

Last year I signed a lease agreement with my friend as a co-applicant and both of our names were on the lease. Then one of our friends move in but was not on the lease because she was only going to be there a couple of months. Both of the other two roommates had pets. They hid it from the complex until I found out and notified the complex. Their animals ruined the carpet and the garage on the property. I received a bill from the complex for the damages, so naturally I forwarded it to the two other roommates. I got a call at work last week from a collection agency saying the other roommate on the lease refused to pay the fee and it is now listed as a collection on my credit report. I have contacted the roommates informing them of the call. but they still refuse to respond. I know I am legally obligated to pay because I signed the lease, but do I have a right to take them to court to pay. I will pay the balance just to get it off my report, but I do not want to be out the almost $800 fee