Not sure how well you guys can see this, but it's a comparison showing the effects on a "typical" TM sized speaker. 8" x 16" baffle with a 1" tweeter centered 4" from the top.
From 0 radius to 1.25" radius in 1/4" increments
Note that the very large roundovers start to change the effects below 3 khz, which is where the crossover is typically found. If the speaker was designed with little or no edge treatment you actually could make things worse using a huge roundover, depending on the design.