Funny reading your post because that is what I have done with my small thornless blackberry vine. I planted it last October between a Knockout rose and a chinese fringe plant, facing the southwest. Five years ago, I planted strawberries in one of the front yard islands and they are very nice looking plants pretty much all year plus the nice strawberries they produce. I hope others can share some ideas.

garden stalker; I have been thinking that they might like the same soil conditions and all but roses are so prone to black spot and I am not sure if blackberries are also, I am going to try it and if I see one black spot on the blackberries I will yank the roses., I think with all the rain that we have had that this year might be a boost for the blackspot and other problems, hope not. On the strawberries that you planted are they easy to grow? I just bought from the store and they have NO flavor yuck. :o) Deanna

Here's what I found:

COMPANION PLANTING:
Not considered a companion plant. In fact it should be grown in areas away from primary gardens and walkways. It grows very quickly and can take over if not pruned frequently.

http://usagardener.com/how_to_grow_fruits/how_to_grow_blackberries.php

Maybe it's not an issue of better growth or stunting growth, but room to grow.

Good luck!

Scarletdaisies, thanks for doing the research, I couldn`t find much, I think I will relocate the roses, I want blackberries. Thanks again.:o) Deanna