can I just drink a martini (Martini Rossi) on the rocks without mixing it?

Well, that's not a Martini.

Martini and Rossi are makers of vermouth, which is used to make the drink called a Martini. (The names are actually unrelated.)

If you'd like to drink vermouth straight, you can. It's good on the rocks with a twist of lime. (Beware, it's a bit of an acquired taste.)

Be Careful! Martini & Rossi is a type of liquor called vermouth. It makes up about 1% of a "martini". The other 99% is either straight vokda or gin.

Yes a martini (99%vokda/gin - 1% M&R vermouth) can be served over the rocks. It's called a "Martini on the Rocks. One shaken an strained into the Y-shaped glass is called a "Martini Up)

Enjoy!

Are you talking about drinking Martini & Rossi Vermouth? God no, Honey!

Sure. You can drink *anything* on the rocks without mixing it. But you can't order it by calling it a 'martini,' because that recipe calls for the inclusion of a liquor like gin or vodka.