3
Because the plural of each flower is given. “Roses” implies 2 or more, “Daisies” implies 2 or more, etc. Otherwise, you would say Rose, Daisy or Tulip.
Thus, it's impossible to fulfill the list.
It can’t be solved. The correct answer is something like, “I want to say three, as that would mean all but two flowers are a rose, all but two are a daisy, and all but two are a tulip. However, you note that I had to revert to using the singular in each instance. There is no bouquet of any size where all but two can be roses plural etc.”
That’s the whole point to the vast majority of this type of interview question. There is no solution, and they’re looking to see if you can articulate why.