You emphasized, "for even their women did change the natural use into that which is against nature."
Could this meaning anything other than lesbianism? For example, if one considers the "natural use" of women to bear and raise children, perhaps not doing so (by choice or biology) would be considered "against nature"?
personally, i think paul means that they were holding positions in society contrary to paul's ideology.
This would be my interpretation as well.
God was quite explicit in Leviticus' "man shall not lie with man as with woman"; I don't see why, if He was speaking through Paul, He would be so ambiguous in Romans.