While you’re at it, take her out on dates. Don’t make the mistake of thinking you can slack on the romance just because you're roomies now. Actually, the opposite is the case.
Now that you're hanging out a helluvalot more often, you need to put extra effort into making things feel special and sexy (rather than boring and too comfortable).
It can be tempting to do the Seamless and Netflix thing every night, but that will drain your relationship's spark. Make dinner for her, or clean the apartment just because, sure. But also make sure you make a grand gesture or two every once in awhile. It will be the difference between having a roommate you just get along with, and a lover who still genuinely excites you.