Read your insurance policy, perhaps ?
****, I am an insurance agent and *I* find those **** things daunting. Most agents I know can't even effectively read an insurance policy. I had some specific training doing it when I was in claims, so I am lucky.
To the original poster, I am guessing that you live in California because your location says Mid*Cal.
Rule of thumb, in CA the policy on the car pays first, followed by the policy on the driver if the policy on the car doesn't have sufficient coverage to cover all the damages. If you guys are/were roommates, be careful that you are not specifically excluded (by name) from each others policies.
Best advice is to call your agent but keep in mind that some agents don't know what they are talking about, sad but true. If you don't have an agent, call the company. MOST agentless company reps don't know what they are talking about when it comes to coverage issues. Be sure to get the name and number of the person you talk to and if they say everything is covered, write them a letter confirming that. That way, if something happens and it is NOT covered, you can whip out the letter. Their word is binding on the company if you rely upon it and suffer an uncovered loss as a result.
While you are on the phone with them, make sure they don't limit the $$$ they will pay for custom equipment (like stereo equipment). If they do, schedule the equipment (if they will let you) or switch companies.