Answer: If you are able to grub out the juniper roots (these may be deep as well as woody) then you should be able to plant there, or at least plant in between where the junipers were.
Roses do best in a location with at least six hours a day of direct sun, in a soil that is well drained and also fairly high in organic matter. Your soil preparation would then include loosening the soil and adding organic matter such as compost, well rotted and aged stable manure and bedding, old rotted leaves, etc.
The pH ideally would be roughly 6.0 or between 5.8 and 6.2. You would need to run some basic soil tests to see if there are any special amendments or adjustments that need to be made as well as determine how much (if any) fertilizing you might need to do.
Your local county extension should be able to help you with the testing and interpreting the results with an eye on growing roses. They may also have suggestions as to specific varieties that tend to do especially well in your local area. Enjoy your new planting!
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