I have been married for almost five years to an immigrant. He recently visited his home country before adjusting his status. My question is, what kind of visa does he need to return back to the states. I am a citizen btw.

You can sponsor him for IR-1 (immigrant) visa by filing I-130. You also have an option of sponsoring him for non-immigrant visa K3 at the same time... and see which ever goes through the system faster.

What was his status before he left? Were forms for AOS submitted?

No he hadn't filled the forms - we just got lazy.