You can say roger isn't equal to garp, but it's clear who oda intended to be the strongest of the old gen
たった一人でガープや センゴク、白ひげ・ロジャーと渡り合う 実力者。 "A talented person who can compete with Garp, Sengoku, and Whitebeard Roger alone." Garp and Sengoku are on the same level as Whitebeard and Roger factually confirmed