Sounds to me like your Roomba is in need of a trip to the vac shop for repairs. Probably, mostly what it needs is lubrication. All vacuums work in what is arguably the dirtiest places in the home, other than the bathroom. And for the most part, they are simply neglected. Your friendly local vac shop will take it apart and lubricate it in places you've only dreamed about, (just kidding). It sounds like it just needs some normal maintainence. It shouldn't be too painful on the wallet.