Sometimes tires will be front and rear specific, with different tread that's optimized for traction, acceleration, stopping ability, etc. Otherwise, you can run the same for either.

Can I get a better description of the terrain you're riding? Does rugged street = fire road? Or do rocks = rock gardens? What kind of bike are we talking about? What size wheels (24", 26", 29", 700c, 650b, 650c, etc)? And what frame (different frames will fit different width tires)?