Your renters insurance, or any other insurance, does not cover roommates. You do have the option to list them on your policy for coverage, but expect a more expensive premium.
Keep in mind that if you need to file a claim, you and your roommates have to cosign the payout check. Also, as the policyholder, any claims that your roommate needs to file will reflect on your claims history, which may lead to an increase in your premium.
An alternative is for everyone in the rental to have their own policy. That way, roommates have renters insurance individually and share no liability — a much safer option.