In this verse it appears that Paul is teaching that men can and do save themselves by their own good
works.
But later, Paul shows that no one can nor will be saved by keeping Gods Law; for no one has kept it.
Romans 3:10,20 - There is no one righteous, not even one . . . Therefore no one will be declared righteous in His [Gods] sight by observing the law
All that is said here (in Romans 1:7) is that if anyone does good (conforms completely to the Laws holy
demands) he will be saved.
At this point, nothing is said as to whether or not man can (I.e., has the ability to) keep the Law!