Tochno = precisely, exactly (more often about location, "tochno v tsentr" - "right into the center")
Rovno = straight, precisely (when talking about time, this variant is better: "rovno v 4 chasa" - "at 4:00"; otherwise, it's the same as tochno: "rovno po linii")

These examples cover only a part of meanings. Talking about digital precision, "tochno" is better: "high precision" = "vysokaya tochnost'" (not "rovnost'"!)