Here is my theory. While we can view that WB had an advantage of having devil fruit, maybe Roger never gave WB chance to use his DF. WB usually needs to punch, swing or touch his opponents to make major damage (I don't think I have seen him use his weapon to make quakes). So when WB tries to use his DF, Roger strikes him before he can make quakes. So WB needs to resort to Haki fight instead.