Okay what have done that I washed the rose petals because the rose bush I gotten it from is outside, then I took a paper towel and dry them off. Well, then I put them in a jar, I was planning on letting them dry in jar. Well this be okay to dry them?
Usually drying herbs needs to be done in an area open to the air, to allow evaporation of the water in the petals.
I would recommend either leaving then on a paper towel in an airing cupboard, on a baking tray in a warm oven (not hot, we only want to dry them, not cook them) or if you have a very warm, well ventilated room you can dry them there.
I would not recommend drying them in a sealed container, they will just rot.
You can dry them using a food dehydrator or you can build drying racks out of wooden picture frames and window screen. (It's all over pintrest) Just make sure to keep them away from direct light, harsh smells, and pests/dust.
An incredibly easy way to dry roses petals is to dry the entire flower. Flowers hung inverted with often retain their color and at least most of their shape. I would suggest cutting a few roses, and hanging them by their stems for a few days, maybe a week or two, then plucking the petals.
I have a collection of baskets just for drying herbs. You can line them with paper towel, then loosely cover with another. This will keep dust and anything in the air from getting on them. Sealing them just makes for no air to dry them, so they rot in their own juice. Just some added info that I use.
putting them in a jar like that will make them rot most likely, like everyone above me said you should lay them out on a paper towel and let them air dry. when i do flowers i like to string them up upside down and let them dry that way. a friend actually sent me a link this week of people who took cheep laundry baskets and filled them with herbs to dry them