You should have got this from the faq, but since It's raining and I'm stuck indoors:
Yes, No, Maybe

The roms display the scoreboard, the vpt file displays the actual table. What you need depends on the table.
Old tables didn't have any electronics to speak of, so they had a mechanical scoreboard. Those just need a vpt file and visual pinball.
Newer tables have a dmd display (set of leds used to make pictures). They require pinmame, visual pinball, as vpt file and a rom.
Tables from the late 70's to early 90's used a numeric digital display. Most of these tables use pinmame to emulate the scoreboard, but a few just simulate the scoreboard in visual pinball by using a special font. For some tables, both versions are available.
Long story short, try a game, if it asks for a rom, get it.
