So...why is it OK for angels of God to influence the outcome of games? And why couldn't God detect the sarcasm of Roger's dad's fateful words?
I always saw it as a type of "kill two birds with one stone" thing. The angels influence the outcome of relatively meaningless games (not influencing the game that had major repercussions) to have the coach feel genuine affection for Roger & JP, leading to both of them to get a good home, as well as make the coach a better person. I'd say that God did know that Roger's dad was being sarcastic, Roger didn't pick up on it.
The angels manipulate a game against the A's, who are division rivals and presumably trying to stave off the Angels coming from the bottom of the standings. That's hardly a meaningless game, not to mention players' and coaches' livelihoods rely on performance, which the angels are directly sabotaging for no reason (again, Roger's dad had no intention to come back, so there was no reason to rig the Angels to the division title); critics of the movie pretty much cited this fallacy as one of the film's weaknesses.
Also, seems like a pretty selfish part on the angels; surely, the needs of many (baseball players making a living and working to succeed) outweigh the needs of one boy who lacks a sense of sarcasm?