If you are talking about cross-pollinating two different varieties, there are no guarantees of anything. This is how new roses are developed. Breeders study long and hard the family trees of roses they might use to gain the particular qualities they are wanting in a rose they want to breed.
They then cross-pollinate the two varieties, wait for the female to produce seed, then wait out the cold time frame the seeds need and then plant them. Every single seed will produce a rose entirely different from the next. Thousands of seedlings are raised by breeders, just to find one desirable rose with the characteristics they want. Like entering a lottery.
All the rest of the seedlings are worthless.
The actual performing of the cross-pollination is actually quite easy. The petals and anthers of the seed (female) parent flower are removed. The petals of the pollen (male)parent are removed. The anthers of the male are brushed against the stigmas of the female and then a paper bag is tied around the female flower head. The flower head remains on the bush until it has formed a rose hip that is plump and meaty, but not crinkly.
Bury the rose hips in a pot with some peat moss and leave them outside for the winter. In the spring, bring them in, and squeeze the seeds out of the rose hip into a bowl of water. Any seeds that float are infertile, so only plant the ones that sink. Then wait for them to grow, and see what you get.
The only real control you have over what color you may end up with or any other characteristics, is by studying the family trees and backgrounds of the parent roses.
If you are really just wanting to know about cross-pollination, I hope I have answered your questions. If you are looking for ways to propagate and get more roses the same as you already have, there are much easier ways, and I could pass that on to you. Just let me know!
Have fun!
Val
Sorry, I'm a rookie gardener, but I'm SO intrested. 