I googled the SKS Speedrockers, and I don't know why you would bother with them. To keep your feet and ankles (as well as the chainrings, BB, FD, pedals, and chain) clean, the front fender needs to come down much further toward the ground to block the spray from your front wheel. And that front fender is apparently in two pieces, with a big gap at the fork crown -- which will let spray into your headtube, where it will eventually foul your headset bearings. Those fenders will give you a little protection, but not much.

A really good set of fenders - like Rene Herse or Berthoud, or Velo Orange, if you want to spend a little less - won't weigh enough to slow you down, and will give good protection.

Whatever you get, make sure they have a safety release on the front fender, or that you mount them with ample clearance. When riding off-pavement, you don't want mud or other junk to get caught between the tire and fender - especially in front!