TEXT: Rough Rider regiments are rarely deployed as a single
  fighting force; their specialised skills are instead often
  divided up to support other, less mobile formations. On
  those occasions when they are fielded en masse, they
  present the foe with an inexorable wall of muscled steeds
  that tramples anyone foolish enough to stand in its way.
  Rough Rider Companies rove ahead of the main Imperial
  Guard force, tasked with overrunning and destroying
  isolated groups of enemies. The Rough Riders roam the
  landscape in search of the spoor of enemy formations and
  can track their quarry for days if necessary, awaiting the
  perfect time to strike. Of all the Imperium’s Rough Rider
  regiments, it is those from feral and barbaric worlds that
  excel at this kind of warfare, warriors that are used to
  operating as independent, nomadic bands of hunters.
  However, the warrior pride and tribal mentality of such
  regiments often leads them to pursue ever greater glories
  and take ever greater risks. Though bloody and costly, some
  of the greatest victories in the Imperium’s history have been
  won as the result of a Rough Rider Company’s reckless
  charge. 
  When a company of Rough Riders commits to the fray the
  results are as deadly as they are terrifying. The Rough
  Riders themselves are heard before they are seen; the land
  itself heralds their arrival as the beat of hundreds of hoofs
  sound like an ominous war drum. The growling tremble of
  the ground is soon joined by the war cries of the riders,
  lances lowered as their mounts gallop towards their quarry.
  ROUGH RIDER COMPANY
  POINTS: 100 + MODELS
  Special Rules:
  Strike Force: All units in the formation must be deployed within
  6" of the Rough Rider Command Squad, or, if coming on from
  reserve, they must enter the table within 6" of the point
  entered by the Rough Rider Command Squad.
  Outriders: Rough Rider Companies use outriders to scout the
  land and are famed for tracking and encircling their foe. A
  Rough Rider Company has the Flank March strategic asset.
  Born in the Saddle: All Rough Rider Units within 6" of the
  Rough Rider Command Squad have the Skilled Rider rule.
  Run them Through! At a roared command, the Rough Riders
  lower their lances and gallop into a thunderous charge. In any
  turn in which the Rough Rider Commander charges into
  combat, all units in his formation within 6" gain the Furious
  Charge ability and receive +2 bonus Attacks instead of the
  normal charging bonus.
  FORMATION: 
  1 Rough Rider Command Squad*
  5+ Rough Rider Squads
  *A Rough Rider Command Squad is a normal Rough Rider
  squad with the Rough Rider Sergeant designated as the Rough
  Rider Commander. The squad has the option to upgrade one
  Rough Rider to carry a Regimental Standard for +15 points.
  ROUGH RIDER 
  SQUAD
  ROUGH RIDER 
  SQUAD
  ROUGH RIDER 
  COMMAND SQUAD
  ROUGH RIDER 
  SQUAD
  ROUGH RIDER 
  SQUAD
  ROUGH RIDER 
  SQUAD
  “I have seen war in all its forms. I have seen feral world savages
  braining each other with stones, and I have monitored the death
  of a whole planet at the hands of a virus bomb. I have seen
  Space Marines drop to certain death, and win. I have seen Titans
  crush whole platoons underfoot. But there is no more stirring
  sight in war than the charge of massed cavalry.”
  
SOURCE: textdata/thevault/Warhammer/40k/1st-8th Editions (Prior)/5th Edition (2008)/Apocalypse Datasheets/40k 5e - Imperial Guard - Rough Rider Company.pdf