Sorry about your father and sorry that no one has responded earlier.

My actual experience is strictly with air-drying roses in a hot environment. This produces good results for many purposes, but there is usually a color shift and a lot of shrinkage. Silica gel would do more to preserve the color and size of your roses. You can find many descriptions of how to do it on the web.

An alternative is freeze-drying, but it is quite expensive and it's not easy to find someone set up to do it (it is definitely not a do-it-yourself-in-the-kitchen procedure). A little searching might turn up someone in your area who does this, though.

I'm so sorry for your loss... I did the same thing when my grandfather died and then when my grandmother died, I then combined the flowers and made a wreath... but what I did to preserve was put them in kitty litter... I, ever so carefully, put kitty litter inside the roses (to maintain shape) and then I buried them... it maintains color and size... I've tried the silicon and wax before and it destroyed some of the flowers, of course I tried it on flowers I'm sure weren't meant for it, it was like it melted the flowers (my aunt and I decided to do it with daylilies, it was what we had at the time, and you should've seen the lump of flower and wax, yuck :) )... I'm sure this post is to late, and I hope that whatever you chose to do worked well... let us know how it went... this post, I guess, is for if you ever decide to preserve flowers again... I've done this technique with gladiolus, orchids, gerber daisies, roses, and many other flowers, it is my favorite method... keep us posted, and again, I'm so sorry for your loss.
Brittany