I've ridden up Ventoux twice. It's never incredibly steep, but it's very long. I'd definitely do it on your road bike.

Most folks would want either a compact or a triple for it. A 50/34 front, and 11-28 rear would be adequate if you're in reasonably decent shape.

Find a 10% grade somewhere, and see if you can ride up that in your lowest gear, without an uncomfortably low cadence. If you can, you're set.

If you can't, then you need to get lower gearing, by going to a compact, a triple, or a bigger cassette in the back.

Bigger cassette in the back may require a new rear derailluer. You might be able to borrow your MTB rear derailleur, and then you'd just need a cassette and chain.