I don't have seeds to share yet, but my brother sent this to me.
Optimum time is in the morning just after the dew has dried.
You can use petals that have dropped on the ground, i.e. after a rose has 'exploded' as my kids say, but don't use any brown edges of the petals. I just snip these off with scissors. Take the rose petals, you can mix colors as they are all going to turn to a dark shade of ebony anyway and you can mix scents too if they are compatible, and put them in the chopper dish and chop until very fine. Take out that bunch and put in a glass jar and continue chopping the rest of the petals a dish full at a time. Put them all in a glass jar and cover loosely.