Loaded tests are always harder on the power supply. This is why many cheap power supplies power a low powered system fine, but fall out of spec at higher loads.
Rosewill's power supplies are getting better to be honest.
12V ±5% MIN 11.40 MAX 12.60 <-This used to and MAY still be 10%, but I would like to see less.
5V ± 5% MIN 4.75 MAX 5.25
3.3 ±5% MIN 3.14 MAX 3.47
-12V ±10% MAX -10.80 MIN -13.20 <- I know it looks strange, but I think that is how it should look
+5VSB ±5% MIN 4.75 MAX 5.25
Also important is how much the voltage fluctuates and ripple in the voltage. Cheap testers will NOT check that.
EDIT to reply to your other post.
Reviews sites use huge banks of resistors to eat the extra power(and feed all that heat back into the power supply for extra stress).
For you, get an OLD system and as many hard drives and other hardware as you can
, unless you want to built a load tester, you would need some heavy duty resistors(hmmmm 12 volt electric car heater rated at 10 amps or 120 watts
. This does not load the lower rails, but most newer power supplies get those off the 12 volt rail anyway) to make the kind of load a power supply can power.
I can NOT recommend playing with power or wiring in a car heater