If Cullen wants to go to the Inquisition, Alistair's of the firm belief that it's safer if the Inquisition comes to him. An apostate as concerned with staying in hiding as Cullen won't have been tested much, he suspects, and years of watching over mages can't compare to reaching for the Fade yourself. Yes, Cullen's made it this far alone, and he's still got that sword at his side --

But Thedas has rarely been kind to mages.

And Alistair's feeling -- protective, after receiving so little protection from Clarel in the end.

"It's a big cave." Gentler. "Plenty of room for two." He points to Cullen. "If you snore I reserve the right to throw half my bedroll at you, though."