If you have a press and a piece of 3/8" diameter round stock you may be able to create the beads by placing the metal on top of two 2x4 pieces spaced 3/8" apart - use a piece of plywood underneath and some wood screws to hold the two 2x4 pieces at the correct spacing. You could bevel the upper edges of the wood at the gap with a sanding disc so that the rod will fit down nicer in between the space between the two 2x4 pieces. Set the sheet metal in the proper spot in the press and begin to push the round stock downward with the press ram at one end and then move over about and inch at a time. You may have to make a U shaped pusher so that the rod does not try and roll as you apply pressure and it may take a little while to form the bead trough but should work. Can try a scrap piece of metal first and see how it looks.
Could also check with someone local who does furnace / AC duct installation as they may have a bead roller.
Just a couple of suggestion that may help