There are a lot of roses in my garden at the moment and I've been wanting to make rose-flavored turkish delight. Looking online, most recipes for rosewater appear targeted towards using it as a cosmetic fragrance (rather than a food ingredients). I know that flowers can sometimes be toxic or gross if not processed in the correct manner / generally chowing down on flowers from the garden is ill-advised.  Other than washing the roses, are there any particular considerations in ensuring that homemade rose water is food safe?  Which roses should I use if I have access to several varieties (e.g. white/red/pink)?   
The biggest issue with what's essentially a foraged food is identification.  Luckily for roses that's quite easy.  You do need a lot of petals, and well-scented ones; many pretty varieties are bland, but wild species can be very good.  Scent is crucial, colour is optional, but (pale) pink rosewater is traditional and is what you'll get if use use a mix of colours including a little red or plenty of pink. The link above says that all rose petals are edible, a statement I've seen elsewhere too. Cultivated roses, or those in hedges right next to farm fields, may have been exposed to pesticides.  In particular those pesticides used on ornamentals may be long-lasting and not wash off, unlike those used on crops.  That would rule out roses bought as cut flowers, which are almost guaranteed to have been sprayed. If you've grown them yourself and know they've not been treated with anything that isn't suitable for use on food crops, then a good rinse and inspection for bugs is all that's needed. Some recipes start with boiling water and soak, some simmer, others do something close to distillation (that recipe doesn't use many roses, and probably makes very little). I once made a very small quantity using white dog roses and the traditional simmering recipe in (I think - it's at home) Jocasta Innes' Country Kitchen - you really do need a lot of good fresh but ripe petals, ideally just before they start to turn brown. Storage - unless using quickly I'd freeze it (in ice-cube trays perhaps); lifetimes in the fridge aren't well-established for home made versions and we can't extrapolate from commercial preparations. 