Typically when you are going to have a roommate or other financial assistance it has to be in the form of a contract. The lender is going to say that since the others are not on the loan application they are not responsible for the debate. This means to them that they are going to look at your capacity to repay the loan.
Your roommate could decide to move out. Your family could encounter some things that would change their ability to assist you. So the lender is going to look at that and say, can she pay on her own?
You might be able to include the rent payment from the roommate IF you have a lease/contract set up. Just depends on what the lender says. And I definitely agree with talking a lot to your lender. Most banks are what is called A paper credit. You might do better going with a broker, especially one who specializes in sub-prime lending. Just communicate a lot with the lender so they are clear on your situation and what you are wanting.
I hope that helps.