From rough you need to add some additional stroke strength (yardage) and expect more run after the ball lands.
How much the rough effects your shot will vary by the depth of the rough and which club you use.
The deeper the rough is and the longer the club you use the more rough will effect the shot.
With a 64° wedge and 20% rough there is little effect from the rough. With a 3 iron I add 7% of the yardage of the shot with 20% rough and expect 50% more roll on landing.
With 30% rough and a short club I add 15% of the yardage and with a long iron will add 20% and expect even more roll. When the rough is 40% it gets even more uncertain. For short clubs I add 20% and with long clubs the extra, extra roll brings fairway and green undulations into play big time.