Hello Bruce,

The good news is that rose rosette disease does not affect other species of plants. Your forsythia must have another issue. 
We can try to help with the forsythia.
1-Please attach two forsythia pictures, one taken 5-6 feet away so the whole forsythia is visible.

2-Take a second picture close up, from about 12 inches away, of a diseased branch.

3-Describe what care you have given  the shrub- how much you water it,  fertilizer, or any chemical sprays applied to the shrub. 

4-Were there any sprays or other chemicals applied to the grass or other plants near the shrub?

For roses, you must remove all rose roots and any other debris of the diseased roses, and then search the area for any wild roses ( “multiflora rose”) and remove those, too. Here is information on rose rosette disease:

https://hgic.clemson.edu/factsheet/frequently-asked-question-about-rose-rosette-virus/

https://www.oardc.ohio-state.edu/weedguide/single_weed.php?id=87