Gather branches that are all between 1 to 2 inches in diameter. Cut side shoots from the branches to leave as straight a branch as possible. Measure and cut the branches until you have 4 branches each 6 feet tall and 9 branches all 2 feet long.
Lay the four 6-foot branches side by side on the ground running vertically with each branch set approximately 6 to 7 inches apart. Starting at the top, place a 2-foot branch horizontally across the top cut ends of the 6-foot branches.
Screw through the 2-foot branch and into the 6-foot branches at each of the four intersections to connect. Place the next horizontal 2-foot branch 6 inches below the first and secure with screws.
Continue to place the 2-foot branches 6 inches apart and screw them into place until the entire trellis is constructed and the bottom 18 inches of the 6-foot branches are left sticking out from the grid-like frame.
Loop lengths of twine around each intersection of the trellis to cover the screws and create a rustic, natural look, if desired.
Dig a narrow, 1-foot-deep trench behind the area where your roses will be or are planted. Make the trench 2 feet long. Slip the bottom ends of the 6-foot branches into the trench and hold the trellis so it is level. Fill in the trench and pack the soil around the trellis to hold.