Flowers of course include roses, but there will be mostly bases of other flowers in the flower challenge. Both themes will be done eventually, it's just a question of which you want to do first.
The base challenge will run outside of the normal challenges, you will have to find your own source images, there will be no theme, you can enter up to three bases, there will be voting, the special category will be Best Crop and the bases will be used for a new challenge, unless you specify you don't want your bases to be used.
Allow fandom for the base challenge?
Nine days left to enter: Challenge 168 - Birds