Is there a way to set up the roster requirements such that a manager can start 1 RB, 2 WR and then 2 Flex (WR or RB)?
It is against Fleaflicker's terms of service to post offensive material.
The commissioner should select "Custom" from the roster requirements page.
You can start 2 Flexible Offensive players and set eligible positions to be WR and RB.
Let me know if you need more help with this--it should be very easy to do.