Create a large, solid surface workspace where all supplies and tools are easily within reach.
Prepare the terra cotta pot by adding the bag of gravel or rocks to the bottom. If possible, use a weathered terra cotta pot with a slight white patina. Place just enough gravel or rocks in the bottom so the terra cotta cannot be seen. Do not overfill. This will provide support to the topiary so it does not fall over.
Take one craft foam ball and trim 1/4 inch off the bottom of the sphere with a knife. Discard the cap. Wedge the sphere into the base of the pot. Trim excess, if necessary, so the sphere is a firm fit.
Stick the base of the wire topiary form into the foam in the pot until it reaches the bottom or has adequate support. Cut the other foam sphere into four slices (this will allow it to be placed into the sphere). Wedge each piece in, bottom first, and apply a layer of hot glue in between to reform the mold back together. Cover the foam with a light layer of hot glue, being careful not to get glue on the frame. Add enough moss to cover the foam. Repeat at the base where the foam shows through.
Take each rose by hand and proceed to cut at a 45 degree angle, just below the green, about 1/2 inch down the stem. Run under cold water. Discard the remainder of the stem. With bud in hand, begin to wrap floral wire around the remainder of the stem. Make sure the wire is side by side and forms a strong support. Make sure to leave the bottom of the stem exposed. Once the stem is covered, snip the excess wire with shears.
Remove the lids and begin to fill the floral tubes with water. Replace the lids and start placing each rosebud down into the tube until the bottom of the bud is on top of the lid. Proceed to stick each bud and tube into the topiary. Start at the top and work downward. Cover the entire top with rosebuds. Fill in bare spaces with green moss.
Trim a long stem of leaves from the ivy plant. Place one end of the plant into a floral tube, if desired (for longer preservation). Push the tube into the base, until hidden. Allow the ivy to trail up the topiary to the base of the cone, and secure with a floral pick. Add more moss to cover the pick. Conceal all bare metal with moss and ivy. Wrap a piece of French wired ribbon around the pot, and tie off with a bow. Place the finished arrangement in the center of the table.