am i allowed to hook up w/ my ex-girlfriend's current roommate?

[ua1176]

title pretty much says it all.

i dated this girl for a while. then we broke up. i talk to her once every few months but we don't see each other frequently or anything.

she has a roommate. over the past 2 years or so the roommate has slimmed down significantly and is now fairly attractive.

the roommate comes to hear my band play last night. we go have fun at an after party for a bit and then i drive her home cause she has work early. i get her #. there are some signs that she's interested. she seems like she'd be fun. am i allowed to pursue this?