The Astros' and Red Sox's cheating scandals are much ado about nothing ... so says Pete Rose, who tells TMZ Sports sign stealing ain't that big of a deal at all.
The MLB legend says back when he was playing ... he NEVER got an advantage by stealing signs -- saying he was always worried the guy reading the catcher would be wrong.
"He might not have the signs -- he might tell you wrong," Rose says. "Now, if you're looking for a low-and-away breaking ball, and the guy throws an up-and-in fastball, you just got one off the kisser.