Is there anything on that 10"(?) white border. Is that part of the rose quilt, or is laying another quilt?
If it's part of the quilt already, I'd either put some applique on it, or cut it down. That's way too much dead space, especially if you're going to/want to add more borders. It would just be a huge void. And I usually like wide borders.
As for adding additional borders, it really depends on how big you want the finished quilt to be.
You could use the white fabric you cut off to make some pieced blocks. Flying geese, using the white/pink/floral, is an option to tie the center to the outer border. That would frame the green lattice border nicely.