1. When it is below 50 degrees outside.
2. When something is cool but not really cool just... meh.
1. Tobias: Hey it's below 50 degrees outside.
Bridgette: Since it's below 50 degrees outside, you could say... it's pretty rosy.
2. Dell: Hey I bought a goldfish today!
Glenn: that's pretty rosy... not amazing... but it's rosy.