The Roller Derby is the panacea of the proletariat, the great Un-sport, a smash-and-crash arena of spills where the most triumphant moment means watching good broad Joanie Weston bump bad broad Ann Calvello hard enough in the boobs to drive her over the rail. Where she will hopefully break a leg or at least knock out a couple of teeth. Make no mistake, Derby fans are out for blood; they are also as much of a phenomenon as the show. The Derby grew out of the marathon madness of the '30's. It was conceived by Leo Seltzer whose son Jerry currently holds a monopoly in what Variety recently called ""the fastest growing entertainment attraction in the country."" Its television audience has shot up to 3,000,000. Its players are surprisingly diminutive (one of the toughest tigresses was 4'11"") and surpassingly dull, sharing a penchant for chainsmoking and compulsive haircombing. The fans have been, from the beginning, predominantly female and strikingly savage (one irate woman tossed her months' old baby at an unsatisfactory skater). Mr. Deford presents a lively picture of all this but the real story should lie in the hands of the sociologists and analyists, an interesting study of America the Violent in Five Strides.