You'll need to allow longer stems cut on a diagonal slant for the roses farther away from the center.
Apply glue to the entire stem.
Slide into place from the longer end point of the corsage. Keep in mind you usually need an elongated (oval) shape for a traditional wrist corsage).
The gaps between the roses will be eventually filled with other flowers.
I add more glue to another rose stem.
Then insert it into the opposite end of the corsage in the same manner as before.
The corsage is rapidly taking shape.