High Aspect Ratio Trussed Brace Wing | Kerbal Space Program 

Imagine the torque produced by those wings

The best ksp question “how big can we get”

the reason it might be pitching up during roll could be due to the v shaped tail. if you turn off roll authority for the tail control surfaces it might be more flyable

i love high AR planes! id check your center of mass and center of lift if i were you. my guess is there isnt enough lift from the tail so perhaps you need to move your center of lift back.