Continue filling in the design, inserting the stems angling towards the center portion of the bouquet.
How close you get is going to depend on the size and shape of the roses. That's why I put a bed of the tree fern under the roses - helping conceal any foam.
If you don't want anything to show, consider placing smaller spray rose heads in between the standard roses.
Work your way around the center roses in a circular pattern.
The center roses should face straight out, while the outer roses begin to rotate outward.