You may to check with the Etsy seller - that person is likely the designer and may be able to answer your question. I can see from several people's blog posts about the quilt that it is all strip pieced, but I don't know exactly what width strips it uses.
That said, I like math puzzles, and your question can be answered with math. (Caveat: I will assume that the pattern calls for 2.5" strips of the background fabric.) The pattern calls for 3.25 yards of background fabric, which gives you 117 inches. When you cut that length into width-of-fabric 2.5" strips, that will give 46.8 strips, so round that down to 46. Jelly rolls often (but not always!) contain 40 strips, so if that matches your jelly rolls, you need two jelly rolls, but you won't need many strips from the second one.
Looking at the pictures of one of the blog post entries, I can see that the background is made up entirely of small squares sewn together:
Personally, if I was going to make this I would be tempted to modify the design use larger pieces away from the snowflake. I raise this issue just so you can consider whether having many small squares through the background appeals to you or not. (I don't know whether you are thinking of doing your strips so that strips/patterns are split up all over the quilt, or if you want to have many squares of one strip/pattern are all in a line.)
Correction: The background does have some half-square triangles mixed in, but I expect you got my point.