Roses are great for cooking and baking! In middle-eastern cooking, rosewater is used in a lot of recipes. It has a pretty strong floral smell and taste, so use it sparingly if you're unsure. Rose petals are edible and, near where they connect to the flower, a bit sweet. You can dip them in simple syrup for a pretty, edible garnish on a cupcake! You can also dry and powder the petals, which adds little to the flavor of a plate, but looks like mineral dust, which can be very pretty if used properly.
Hope this helps!
To make your own rosewater, buy a couple dozen roses on the cheap, remove all the petals to a large glass bowl and steep them in water you boiled and cooled for a minute... About 104 degrees Fahrenheit. Steep until the water is completely cooled, you can't oversteep rose petals, then discard the used petals (they won't be very pretty anymore, sorta water-logged) and bottle the rosewater in a blue bottle to protect the essential oils you just extracted from the petals, from the damage the sun can cause.
Or you could just buy a bottle!