Besides, I'd expect the female functionality to cease at the certain age, while male functionality to continue for much longer.So, it is reasonable to expect the young people to play a female role, and then switch to a male one.
In my society self-impregnation is outlawed taboo and hermaphrodites who want to have children must have a partner.
Many of these partnerships are analogous to human marriages and tend to last.
Specialization is an advantage, if one hermaphrodite is much better at making money the family would be better off financially if that one takes the "male" role of only siring children and not having career breaks.
Since fertility rate by age is equal to human fertility rate, there would be more hermaphrodites that could only sire children but can't bear them.
This can be combined with the first option to make it more difficult for someone to have a child (thus be out of the work force for a while) and then resume their career.
Let's not forget that even in same-sex couples there may sometimes be something similar to gender roles, and in heterosexual couples the roles my switch.
Like the thinking that redheads are more aggressive or blondes have more fun.
Since they don't have groups with different sex hormones that might influence one or more behaviors, the groups will likely have less agreed upon differences though.
So a personal preference or natural talents could also play a role.
Since the existence or lack thereof of gender roles is something that perpetuates itself, I think it's a matter of equilibrium.
Which gives some interesting cues about family pattern. I do not doubt that a visiting human would apply a gender role to anyone from this planet they met based on their aggressiveness or beauty (or whatever gender role baggage they brought with them).