Roses make up a genus of perennials that come as either vines or shrubs and currently have hundreds of proper species and hundreds more in the way of hybrids. Caring for them is something of an art. They have different nutritional requirements than the average perennial, as well as water and sunlight needs. Still, roses can be given the best care and have problems. It's simply of question of identifying the problem and correcting it.
Japanese beetles are attracted to lightly-colored rose blossoms and eat the petals before stripping the surrounding leaves. They eat the rose, but they do not live on the rose. Simply remove them by hand and rake up any plant debris surrounding the rose as that's what the beetles live in.
Thrips are insects that are tiny and orange with elongated bodies. They feed at the base of rosebuds and cause new flowers to bloom deformed and discolored with brownish yellow streaks. To get rid of thrips, cut away any affected blooms and spray surrounding leaves and flowers with lemon juice. They are deterred by citric acid.
Crown gall is an infection of the root, causing abnormal growths called galls on the lower branches and roots through which moisture and chlorophyll bleed away. The galls have to be sliced away, after which the cuts will heal cleanly. If the rose retains its moisture long enough, it will eventually fight off and destroy the infection.
Mosaic is transmitted by aphids. It causes no harm to the rose, but it does create a yellow mottling to the leaves which can be unsightly. Symptoms disappear by themselves.
Black spot creates small black rings on the rose plant's leaves and the leaves subsequently turn yellow and fall off. The infection hides in the branches during winter and returns next spring, so the entire branch must be pruned away to get rid of it. Botrytis blight appears as a grayish brown fuzzy mold that grows on unopened buds.
Opened blooms are flecked yellow and brown which wilt soon after changing color. This type of fungus affects all parts of the rose plant but only manifests in the blooms. There are no other treatments but to remove the entire plant so it does not infect others.