The answer, in most instances, is “no,” even though some insurance companies allow it.
Renters insurance covers your belongings, along with providing protections for loss of use, liability, etc. Roommates are not included by default on a policy, even if you’re both on the lease. Also, there’s no “insurable interest” between roommates, which means they typically don’t have any financial interest in your stuff, and you don’t have any in theirs.
To put it another way: If you didn’t renew your lease, you’d take your things, and they would take theirs. It’s not like a divorce, with a lot of shared property. (Although maybe you’d both fight to take that rice cooker you bought together and never used).
Here are three reasons not to share a renters policy with a roommate: