Replying to guys... what's the deal

Ok so here's the issue: my roomate met this guy like a month ago, has gone out with him a 4 times. Last night he took her out to a super fancy dinner. they've made out a little but that's it. they've never talked about whether they're 'together' or not. so are they going out or what? and is he ever gonna bring it up or is it up to her? why are guys so complicated?
oh ya and she's 18 hes 21 if it makes any difference.
thanks!