I continue to wire and tape several more roses for my corsage. Keep in mind the size of your wearer. A tiny, petite person would need a smaller corsage - perhaps even considering using spray roses instead of standards.
Roses should have a firm feel to the head. Loose petals can be a sign of aging and the corsage may not last long after it is pulled from the refrigerator.
Cut the stems off short (about 1" to 1 1/2" below the caylx) with a sharp knife. Scissors can have a hard time cutting through the tough, slippery skin of a rose. Be sure to remove any thorns.
Cut and tape all the roses and other flowers (including greenery) and tape before beginning assembly. This makes a quicker production, as you are not continually picking up and putting down your knife.
I keep a stiff base of dry foam close and push the taped components into it rather than lying the flowers down on a table surface, which can cause bruising of delicate petals.