You know, every relationship has different dynamics. Being with someone of the same sex excludes the "traditional" gender roll of the absent sex, so the definitions are up in the air. In the end, people are just people. Every couple, gay or straight, sets their own roles. I've known plenty of straight couples where the woman takes the lead and the guy stays home with the kids, or where they both work, and equally share in decisions and housework (etc..).
Homosexual couples set roles in much the same way as a straight couple - by getting to know each other and deciding who gives what and who takes what. It's not something most people discuss, it just kinda happens as the relationship goes along.
If you really are curious about this, I hope I answered your question =)