The best method to have healthy roses is still the simple trick: just grow them by natural methods. Don’t get upset when they get a few pests and insects. Even if you spray them with chemicals, they will get infected. So leave them alone and just pick out the insects by hand and crush them.
One organic gardener called Jewell M. Richerson had some tea roses in her garden which she protected with a fine mesh poultry wire and then filled half full of leaves which she raked from the yard. Hundreds of ladybugs live in the mulch through the winter. Instead of burning the leaves, as most gardeners do, she put the mulch in her vegetable patch between the rows and the bugs helped to keep pests away. She always has a border of flowers around her vegetable garden, so the mulch she uses on them also contains these helpful insects.From: The Organic Way to Plant Protection. (Rodale Press).
The problem with spraying chemicals is that they also kill the helpful insects which we should safeguard so they are there to deal with the bad pests.