Here is a conversation excerpt:
"バラの花" seems redundant to me. There is no reason to state that a rose is a flower. Does
also sound natural?
If "...バラを貰った..." does not sound natural, then my conjecture:
(-) "バラの花束" definitely means more than one rose.
(-) Maybe does "バラの花" explicitly means just one rose?
(-) And, "バラ" by itself could mean one, or many, roses?
note: That the daughter had initially received just one rose last year, instead of a bouquet, was central to the larger discussion that they were having.