Complex sentence: Slaves were considered as "res", as things, and could be freely used for any activity otherwise illegal, even though, other than opposite-sex activities, same-sex activities with slaves were not encouraged as a form of sexual pleasure.
Split into simpler sentences: Slaves were considered as "res", as things, and could be freely used for any activity otherwise illegal. Other than opposite-sex activities, same-sex activities with slaves were however not encouraged as a form of sexual pleasure.