The TT030 supports standard VGA output at 640x480 at 4-bit color depth (16 colors). No special adapter required, it just plugs into any VGA monitor.
There is a special black and white high resolution mode that's available but only if you have a special monitor (Atari TTM195). It's hardly worth keeping a bulky old CRT around just for this though!
NetBSD also supports some video cards for the TT030, but I'd recommend using your VME bus slot for an Ethernet card instead.