Rossi completed a second test on a road bike at Misano on Tuesday, having made a shock early return to the track the previous day.
He covered 20 laps during two hours of running on Tuesday afternoon, and a Yamaha statement said he "wrapped up this second day of testing with an improved feeling and a more positive impression compared to yesterday".
Yamaha added Wednesday's examination was intended to "verify the positive rehabilitation progress experienced in today's session", and that Rossi would make a decision on whether to ride at Aragon afterwards.
Rossi broke his right leg when doing motocross training at the start of September.
A recovery period of at least a month was initially suggested, and Yamaha ran just one works bike for his team-mate Maverick Vinales in the last MotoGP event at Misano.
Yamaha has lined up its World Superbike rider Michael van der Mark as Rossi's stand-in for Aragon if he is not able to compete.
After missing the San Marino Grand Prix, Rossi is 42 points behind championshp leaders Marc Marquez and Andrea Dovizioso in fourth in the standings with five races remaining.