WB was the only one to evenly match Roger means that no one besides WB can evenly match the dude which means that anyone besides Roger was below WB and anyone besides WB was below Roger.It isn't even hard to understand so Garp was/is/will be < WB and Roger.
End of the day: Roger = WB Slightly > Garp so ya,he is one the same level as those dudes but loses to anyone of them in a one on one battle.