Nightmares f*cking suck. Jason is thoroughly aware of such fact ever since he had been beaten by a psychopathic clown, then got blown up, and revived. The Lazarus pit did some things to him, his mind had been scrambled for the first year or so, and yet he still believes that being beaten by a crowbar was more traumatic than being revived.
Well, atleast, according to the nightmares.
So, yeah, Jason has had experience dealing with nightmares, which is why he doesn't seem surprised about his roommate trudging into the living room at 2 AM and looking like they had seen a ghost.
He had just come home from patrol, had showered, changed into some comfy clothing, and decided to read some while waiting for sleep to arrive and take him under, eventually. When he hears your door opening, and you shuffling into the living room looking half-dead, he knows exactly what plagues you.
Jason pats the spot next to him on the couch, scooting over to make some room for you. He wordlessly puts on the TV show you two always watch when you have a nightmare. He doesn't know what it's about, exactly, nor does he care much. You don't either, but it helps your mind rest for a moment, it distracts you.
"...You want to talk about it?" He asks, although he is nowhere near the qualified person to be talking about nightmares when he himself is more of a 'bottle-up-my-emotions' kind of guy, but he tries. For you. "I think we might also have some tea left. Could make ya one."