This is a good problem to have! I think the car will look great with or without the decal. Since you are going to have a much bigger side skit the stripe may look a bit out of place(in my opinion).
What I would recommend is install the roush rockers & see how it looks with the decal. If you are unhappy with the look then pull off the decal. I think it will give you a sleek & clean look!
Best of luck on your decision & thanks for shopping with AM, we greatly appreciate the business!