I guess there are two ways you could look at this.
One view is that the rifle was planted on the TSBD to frame Oswald and the rifle was planted on the Butler roof to frame Crooks.
The other way to view it is that neither were Oswald nor Crooks were framed. In other words, in the same way there is a straight forward explanation for Oswalds rifle being on the TSBD 6th floor (he brought it in wrapped in a paper bag), there is a straight forward explanation for the above photo of what appears to be Crooks AR-15 rifle being so far away from Crooks body on the roof. I don't know what that explanation is for Crooks rifle yet, but i'm sure one will be provided in due course.