Complex sentence: Not much is known about Roll compared to the other characters, except she was designed for housekeeping instead of fighting, and she is the (seemingly) younger sister of Mega Man (although other sources indicate they are "twins").
Split into simpler sentences: Not much is known about Roll compared to the other characters, except she was designed for housekeeping instead of fighting. She's the younger counterpart of Mega Man (although other sources indicate they are "twins").