Not at all. It depends on a lot of variables, some of which are things like the type of rose, the climate the rose is being grown in, the type of perennial, the overall effect the gardener wants, what the prevalent disease pressures are, ... you get the idea.

Tons of people grow roses in mixed perennial beds all the time. It shouldn't be any problem unless those roses have been overgrown by the other perennials. In which case the perennials should probably be cut back not the roses. Plenty of water shouldn't be a problem unless the soil is very soggy wet all the time. But that wouldn't necessarily cause rust but more likely yellowing leaf drop. If you could post a picture of this bed and the roses it might help us make a better determination of what's going on.

And PARTICULARLY, as Mad Gallica notes -- THE TYPE OF ROSE . . .

Some roses are inclined to rust, while others are not.

If they are the former, they might rust even standing in solitary splendor. The answer might not be removing the perennials, but changing the roses out for more disease-resistant ones.

Jeri

I like to be able to get in and weed around all the roses. With a good spraying program or disease resistant roses, they will actually grow and bloom vigorously when packed rather closely together. But, a major concern for exhibitors is that you will lose leaf set--which means that that particular stem can only be used in classes where foliage isn't a factor.