That red color in beer is a tough one to nail. I've bounced all around it with various recipes, and none have finished exactly where I had hoped in terms of color. I've had some that were dark reddish, and orange-red, and brown-red, but none have been that beautiful ruby red (yet). Odell Isolation Ale this year is a decidedly 'RED' color if you don't pour in the dregs.
From my experience in seeking a solid RED, I've determined that the beer needs to be very bright (near brilliant) to showcase the red color. So much so that I would sacrifice a little flavor and body with finings just to ensure the clarity was spot on - granted, I've never hit "spot on".
The color malt choices also need to be pretty tight, and need to mesh well with the other color malt contributions. A little too much orange in one malt and you've got brownish-reddish ale; a little too much dark malts and you've got brown-amber ale; a little too little color and you've got orangeish ale. Starting minimal and making subsequent batch adjustments seems like the ideal place to start. Three malts is probably an great place to start like goschman suggests.
In regards to roast malts for color, I would caution against midnight wheat for finding your 'red' color. I've used it a couple times for this purpose and each time it pushed things into a solid 'brown' category. I've made a hard rule for my brewing that midnight wheat is only used for coloring beer into the brown side of things, I have to look elsewhere for red. UK Crisp Roasted Barely in very small amounts has some red color to it, but use too much and the bits of roast character can be perceived, as I've experienced on a few batches. Black Patent is said to give some red in small amounts as well, but I've never played with it myself.
So there you go, more information to add to the already tough decision. I'll be interested in what you finally settle on and how well the 'red' color pans out.