There are a couple of ways to approach this.
- The easy- Remove the rose head from the stem and stick the whole flower into a bowl of water. This will require outer petal removal about and hour in so the inner petals can get to the water.
- The dangerous- remove each petal from the dried flower and add them to the water. This is kind of hard to do and you can easily break petals. Especially in the center where they are so close together. Be careful when you get to the center, all the dried insides (stamens and pistils) are a pain if they get into the water.
- A combo- Start off by taking the whole flower off the stem and twisting the stem area while holding the flower. This will loosen the flower petals from the green part that holds it together (forgive my lack of appropriate rose terminology) and will keep the shape of the rose. Take off the bottom and pour out the stamens and pistils to throw away. Put the flower head into the water. Taking them apart this way allows the water to reach the inside as well and you won't have to painstakingly remove petals every hour. Soak them for a good two to three hours, moving them around often and taking off any petals that have already been revived.
Keep the petals in the water until they are pliable and feel like they were just plucked from a fresh rose. This does happen I promise, but it could take a few hours. They will repel the water for quite awhile, but be patient.
When some petals become pliable enough, move them to a piece of cardboard or a stack of paper towels. I steal pre-cut cardboard pieces from the trash at work. Or even better-- dry them off with paper towels then lay them on the card board. When a piece is full add another piece and stack them up with petals.
Once you've finished stacking place one more piece of cardboard on top and add a couple of heavy books to the top. Now forget about it. Really... just leave them be for a week or so. When you are ready to remember about them you will have pressed rose petals that you can add to paper, or bottles for decoration, or any other kind of crafty thing you can think of.