Rockers is generally meant to describe the then newer sound of reggae, from around the mid '70s until the end of the decade when riddims generally became sparser and often slower, and lead to early dancehall.
It was a sound that was defined and influenced a lot by Sly's drumming, IMO. Channel One studio was renowned for this style and I believe the drum sound they got there had a lot to do with it, as well as the house band being the Revolutionaries.
Rent the movie 'Rockers'; it's a soundtrack of the period, with amazing cameos by the cream of JA's contemporary recording and dancehall artists. A classic in so many ways...Check out the 'takeover' when Horsemouth and Dirty Harry change the mood:
http://www.youtube.com/watch?v=qTq-Q...28DDE&index=35
"I man just dance to the Rockers!"
It was also loosely used to describe whatever the new sound in reggae was for a while, but this usage has dropped off.
Some examples:
Mighty Diamonds, '75, from the album that probably did more to kick off the new style than anything else:
http://www.youtube.com/watch?v=cM5c6097FNs
Jacob 'Killer' Miller
http://www.youtube.com/watch?v=HDEUeT88ajQ http://www.youtube.com/watch?v=5hKiePrCV8o
Linval Thompson 2004, strictly Rockers!
http://www.youtube.com/watch?v=qu5JimxoIgc
Same song, original recorded version + King Tubbys dub. Listen to the incredible bass tone on the dub remix!
http://www.youtube.com/watch?v=MGVYuGNRE_s
Sly and Robbie (or often Lloyd Parkes on bass) as the backbone of the Revolutionaries, The Aggrovators, and other names that different producers used for essentially the same group of studio musicians at the time, redid a lot of the studio One classic riddims, and a bunch of new ones as well, and got a driving, clean and powerful sound with some really interesting new beats and a clean big bass tone with a lot more sustain than was common before. Soul Syndicate was a rival band that also held massive sway during the Rockers period, and mixed a lot of contemporary soul elements to the mix.
The sound ruled for a good five years, evolving into Steppers before the Roots Radics came on the scene and led the way to a different style, usually with much sparser arrangements.
Like all past JA music styles, it remains a common style in the panopoly that makes up modern reggae, with Ska, Rock Steady, Nyabhingi drumming, and even mento finding their place.