My brother's roommate stole his wedding ring--what can he do?

My brother is living with two other guys and a girl, and ever since the girl has moved in, the guys' stuff has been mysteriously disappearing. This girl is a "neat freak," who has gone into the guys' rooms (without permission) to make their beds, and one day, my brother noticed the top drawer to his dresser (that he doesn't open very often) was propped open. He went to open the drawer, and when he did, noticed that his wedding ring box was open and the ring was gone! (He is engaged.) Anyway, he said this happened around the same time she had gone into his room. Another example is when another guy's two brand new bottles of Jack Daniel's went missing, and this girl said that one of his friends had come and taken them. She had no description of this "friend", and when he called around to his friends about it, he found out that no one had come to the house. The latest thing they think she's done is hiked up their cable bill by renting a Pay-Per-View movie. She blamed it on the guys, but according to the day and time the movie was rented, the girl was the only one who had been in the house! The guys are furious and plan on investigating with Charter to nail this girl. My main question is what can the guys legally do to get this girl to give their stuff back or repay them (and especially get my bro's ring back!)? What can be done legally in this case--could they prosecute her even though the evidence is mostly cirstantial?