I’m pretty happy with my Sir Roostley in defense in the following line-up :
Tyr - Kageburado - Sir Roostley - Ariel - Seshat (4500 TP)
That team keeps me at a 50% winrate in the 2600 range, and I think it’s partly due to the pressure that Roostley can apply to the attacking team. We don’t see him much because of Telluria (same class), but he’s pretty decent in the tank position IMO.
With that said, he is still mediocre in offense and I only use him in AW to fill a slot in my yellow stacks. Norns may perform better but I didn’t have the opportunity to take her (them ?) on a test.
Eventually it’s up to you but I don’t regret ascending my Roostley as he is pretty solid in defense. Is he worth putting Joon and the Atomos-Vela center aside though ? That’s the question.