Aromatics from roasted chicken and sauce
Remove all the vegetables and discard, they should have released all their "aromatics" to the gravy

You could press them in a chinois (fine meshed sieve) and extract more juices from them.

Pass all the juices through the chinois into a pot and reduce, and you could add a little bit of white wine to finish up the sauce to serve with the chicken.

When I roast chicken, I usually put potatoes, onions, garlic and carrots (and or other root vegetables) in the pan and they roast at the same time; most of the time, the onions are just too cooked to be served, so either I eat them myself, or just discard them.