There are a few issues to consider in making a rose hedge.

First, there's the question of disease. Most roses benefit from room for air flow around them, and of course, in a hedge, you don't get that.

Second is the question of size/habit. It's generally recommended that you stick to ONE cultivar, so that your hedge doesn't go up and down and in and out. I'd only recommend using two or more cultivars in one hedge if one were a color-sport of the other.

Third is maintenance. With a hedge, you want to be able to groom it as a unit. With many modern roses this would work for the hedge, but not for the roses.
I have seen glorious hedges, both formal (hedge-trimmed) and informal made of Rugosa roses. However, if you are in Southern California, Rugosas aren't a great choice, as they like acid conditions, and much of Southern CA is alkaline.

I've seen Chinas used as a hedge -- a continuous-bloomer such as Sanguinea would work well. And we have made a huge informal hedge of a row of 6-8 Golden Celebrations. But Grandifloras would not be my first choice for hedging.

Jeri

What about the J&P Simplicity Hedge Roses? I've never grown them myself, has anyone else? I saw that they come in pink, white, yellow and lavender, and the lavender is fragrant.

'Belindas Dream' makes a great hedge and loves heat.

I think 'Wildfire' is a beauty but you want a shrub type or a floribunda type rose that is full and lush in growth habit for a measure of privacy. 'Wildfire' is typical HT, lots of lollipops on sticks, essentially.

Also keep in mind you'll have a period of time with no privacy when the roses are pruned back.

How wide is the space? Can you do a boxwood hedge next to the fence and then the roses in front of that? You could even do minis with that type of arrangement. That would also give you privacy year-round, no matter what the roses are doing at any given time.

There's a fastigiate boxwood called 'Green Tower' which can be kept to about 12" wide, but gets quite tall, though I don't know how much heat boxwood can take.