I know nothing about JAA ATPL exams, so what I say may only be correct, and not necessarily JAR-FCL approved.
Va may not be less than Vs1*SQRT(n1), which in practice usually means that it's exactly that figure. But, a few aircraft by virtue of clever FBW systems, or good old fashioned aeroelasticity, will offload lift allowing a higher value of Va. The only class of aircraft for which this is often true is weightshift microlights (which are very very aeroelastic), I've not come across any FAR/JAR-25 airliner for which it is true.
Primary flight controls are required by every standard that I know of (which includes all FARs, JARs, BCARs and Def-Stans) to be stressed to the greater loads of full deflection at Va or 1/3 deflection at Vd. This is where the requirement comes from that you mustn't apply more than 1/3 control deflection above Va.
So, whilst technically Va could be different in each of pitch, roll, and yaw, good practice and all the usual standards require that it's the same for each. (I once got away with making it the same as Vf, thus giving the pilot even less numbers to remember, but you don't pull a stunt off like that often).
G