The manual when you get one will have you set it up with elevons with a "Y" harness in each wing to drive 2 servos working in unison. Recomended servo is JR DS-8411.

Some Roo builders have glued the two elevon segments together and used one DS-8611.

elevator travel +/- 25mm )
aileron travel +/- 20 mm ) > all with 20% Exponential ( I use 25 % Expo )
rudder travel +/- 8-10 mm )

CG 100 mm forward of the leading edge of the main spar

On the Roo I just built I used four (4) Hitec HS-5645MG servos one on each segment. Then I used the Hitec servo programmer to set the center and endpoints of each servo to better match surface movments.