Yeah, about recruiting Roman troops in provinces other than Italy,
there are reforms for that.

You are probably still in the Camillan Reforms, so Polybians are next.
To get those, you have to have certain cities under your control;
refer to https://forums.totalwar.org/vb/showthread.php?t=84854, around the reforms section for that.
You should get those shortly, assuming you have most of the conditionals
fulfilled.

As for the areas where recruitment is possible, the Marian reforms,
the reforms AFTER the polybians, make the AoR for Romani
factional troops much larger; most of the map, in fact.
Refer to the Recruitment Viewer for exact provinces.

Also, out of curiousity, how many provinces do you have?
If you have 45 or more, it will help with getting the Marian Reforms.