Rock came with the Beatles. I'd say they invented Rock when they ignored the boos and catcalls in Hamburg, and continued playing exactly what they wanted until it became more widely accepted. Compared to whatever came before them, they sounded ridiculous, almost a joke,but someone of John Lennon's character didn't seem to care, he even did things like wear toilet seats around his neck to eventually win the harsh audiences over....
But, all the artists you've mentionned, and many more, were inspired as youngsters by the Beatles, and tried to get into Rock. So, Rock, riding the wave of the Beatles, by the late '60's, was saturated with too many good bands. Artists coming after them had to look into genres other than Rock in which to excel, in order to earn a better slice of the pie.
That is why, I think Jim Morrison and Eric Clapton, both tried very hard to get into Blues, when in fact, both did better in Rock. Remember. Clapton left the Yardbirds and joined John Mayall's Blues Breakers even before Cream. He's always played a little of both.
CCR. coming along, too, at about that time, would have become little more than a garage band, compared to the Beatles, had they not looked for their unique style- a Blues known as Louisiana Bayou Blues. Very few big names continue in it, nowadays, except Tony Joe White
The Allman Brothers were clever enough, too, in realizing, they had embarked onto the Rock Scene much too late, In fact, they had already had flopped, (twice), as a Rock Band in the mid-to late 60's, with the "Allman Joys", and also, "Hourglass", so when they reformed got into, "anything but Rock", and originally told everyone that The Allman Brother's Band was a "Jazz Band".
In fact, I think the Allman Brothers might have been one of the the first "Bands", too, because, in the '60's I think the catchword at the time was "Rock Group". Rock wasn't, "band", music, but "ensemble",or, "group" music. They were trying to bury the old Glenn Miller style big "band"/orchestra overrated dance band thing of the older generation.
Robert Plant was always a Blues singer, even before Led Zeppelin. And the Stones, of course loved Blues, and their first two Albums, and B sides of later Albums even are very very Bluesy..