Your question in full: What should be done if you rent rooms in your house and all adults have driver's licenses, but they don't have their own cars? Do I have to list those people on my insurance also because they are licensed drivers with the same address? I think that it will be really be odd if I have to list them.
You should notify your car insurance company that you are renting out rooms in your house. Likely your auto insurance provider will then ask for the renters' driver license numbers and other information on them. This would be true if the people were renters of rooms in your house or roommates of yours in an apartment.
Though it may seem odd to list someone not related to you on your car insurance policy, it is normal for car insurance companies to require a policyholder to list all other licensed drivers who reside in the same household. This means anyone you share the same address with: relatives, roommates, friends or strangers that rent out a room in your house.
People who live in your household have access to your car keys and vehicle, consequently your car insurance company wants to determine what type of risk it is being exposed to.
Once your car insurance company is aware of all your household members, it’s up to state laws and the guidelines of your auto insurance provider to determine if the renters will have to listed on your policy or not.
Since the renters don't own their own vehicle, it would appear likely to an insurance company that the renters may use your car and so will normally want them listed on your policy as drivers. If the renters in your home won't ever be allowed to drive your car, you should see about having them excluded from your policy.
When you exclude someone from your policy it means you don't pay for them as a driver on your car and in return your car insurance company will not extend any coverage to them if they do drive your car. This means if there was an emergency and a renter had to use your car, and was in an accident, then your car insurance policy wouldn't cover the accident due to the exclusion.
If the renters eventually get their own vehicles and own car insurance policies, then it may be possible to leave them off of your policy by merely providing proof that the renters have their own policy in place. You may have to provide a copy of your policy to the renters’ auto insurance company, as well, so they don't have to carry you as a driver on their car insurance policy.