Were Roger and Whitebeard Friends?

They're just friendly rivals. Similar in vein to Shanks and Mihawk. Knowing Roger (he had a similar personality as Luffy, noted by Rayleigh and Shanks himself) he was free spirited. If there was a Yonko at that time that would be Roger, Whitebeard, and Shiki.

Was Whitebeard part of Roger's crew?

Whitebeard reluctantly agreed as Oden himself had wished to join Roger, and Oden and his family joined the Roger Pirates as well as Oden's retainers Inuarashi and Nekomamushi, who came on as stowaways.

Was Roger and Garp friends?

3 His Connection To Garp

Garp and Roger are said to have been at each other's throats all the time before the Great Age of Pirates. However, the two had nothing but respect for each other. Garp has previously stated that despite everything that Roger did, he could never bring himself to hate the guy.