If the guy is in a situation where he just can't afford to pay for things and what money he does have has to go for food, clothing, shelter and the kids then he just can't pay at this time.
If you want to stay with him but not have to pay for everything then by all means let him know that you can't afford to pay for everything and if he can't afford to do something he should let you know so the two of you can think of other things you can do that don't cost so much money.
It may be that this guy just isn't at a place in his life where he can have a GF right now. It sounds like his focus needs to really be on bettering his financial situation and making sure his child or children (don't know if that is daughter's or daughters') needs are taken care of. Right now he's struggling to get through the daily grind of just living and sometimes BFs and GFs are luxuries that you literally can't afford.
Look at it this way:
He's in a bad situation.
Is he handling it well?
Are you able to handle it?
Are you an asset to him or a burden?
Are you his partner and support (emotional/spiritual--not necessarily financial) or a distraction?
Is your presence in his life at this diffult time a relief to him or just another thing that demands his attention?
How he handles himself in times of adversity tells you what kind of person he is. Are you seeing that he is someone you would want to be with when the times are better?
You have to understand, until he gets his finances settled, you aren't going to be showered w/ gifts and treated to evenings out and sometimes you're going to have to pay for all of you. If you want to stay with him then you need to pick and choose what you can afford to do and give him the chance to pick and choose what he can afford to do even if that is homemade pizza while you play board games w/ his kids.
This answer assumes you aren't living with him yet. (you said you had bbeen seeing him for about a year.)
If you are already living with him: then your question says you are roommates w/ benefits and not a committed couple. If you were a committed couple then you would know that it's not "my money" and "your money", it's "our money" and sometimes one of you will contribute more financially than the other because that's just what life throws at you sometimes. In this case, you either need to work up a budget to cover your mutual expenses or you need to rethink your relationsip--is this who you really want to be with forever and ever and the money situation has just now brought that to your attention.
