I would say charge what the market will bare. That being said, what you make is a unique piece of hand crafted ART! So, there is probly not pre-made market to compare with. Part of finding the right price to charge is finding the right Clientele for you to allow to purchase YOUR art work!
I would charge $25 -30 per rose and $65-120 for the Vase depending on how much time you have in to them (amount of tooling)
I would think You could probably contact your local florist and arrange some kind of consignment agreement. Or get hooked up w/ a Florist organization. They pay $55-95 for roses that are dead in a week or 2. Your leather Roses are permanent, will not wilt, rot , go bad. There are people who would pay $500 or more for a permanent display of ones love.
Your customer is not the usual walmart shopper, Your customers are ones who see value in artistic endeavors, and as such are willing to pay to own them. So you will have to find them.... Home Decorators, Florist, Art shows... etc... Do not go Bargain Basement.
my 2 cents.