Yes, it's possible that theroaming connection affected the win percentage, as it might not have consistently sent events to Google Play Games.
As for the absence of a record on the leaderboard, I may have a theory:
If you win with a time greater than your overall best time, the game currently don't prompt you to submit the score online. This is done to reduce the number of server requests, assuming that your best score is already on the online leaderboard. However, in your case, your best time might have been set before the new leaderboards were introduced, or the request to submit your score may have failed for some reason.
To confirm this theory, please open the stats (the button in the bottom right corner of the main menu) and check the best time in reborn hard.