The Roger Pirates were the crew of the late Pirate King, Gol D. Roger, and were the only crew to ever reach Raftel, the end of the New World in the Grand Line.
The few members that have been seen are amongst the most powerful pirates in the current storyline, with Rayleigh being referred to as being 100 times stronger than the eleven super rookies and able to fight Admiral Kizaru to a stalemate, despite being an old man. Shanks over the decades has established a reputation and obtained power, becoming one of the four powerful pirates known as the Yonko. Both he and Rayleigh display powerful Haki abilities.
Crocus did not display this, though it is not known whether or not he possesses the ability.
However, he was not a member of the original crew; he was taken in to keep Roger alive on their final journey. Despite not being an original member of the crew, however, he did display some strength as an old man, stopping bazooka blasts with his own body.
Buggy appears to lack this ability, indicating that even on their crew there was a strength divide. However, even Buggy has attained the status Shichibukai after the timeskip, albeit by exploiting his former crewmates’ reputations.
Kozuki Oden, a member of the Kozuki Family, was also a member of the crew and like his captain, was one of the few people known to possessed the ability to read Poneglyphs. As a result, the crew has not one but two people potentially capable of locating and reviving the Ancient Weapons as a result of their ability to read Poneglyphs.
Upon arriving on Zou, the crew was accompanied by the two powerful Mink rulers, Inuarashi and Nekomamushi, who have been shown to fight on par with Jack of the Beasts Pirates, who holds a 1,000,000,000 Berries bounty.