What will cause a roaring sound while driving down the road?

You're asking for a best guess - in reality that is all we can provide without the vehicle present .. I'm going with a failed or defective front hub bearing! .. 'Possibly' incorrect installation procedure. There are some 'fair' - some that are better - and finally top quality hub bearing assemblies that can be purchased! ... Just saying. I will add - bearing noise can fool even a seasoned technician as to exactly where it is coming from while driving the vehicle .. All four wheel bearings should be considered when testing. Good luck with it!