Justin Bieber's heartfelt video about changing his ways might melt the hearts of Beliebers, but comedian Jeff Ross could care less -- he's still gonna rip him to shreds at the roast.
The Roastmaster General was just getting back to L.A. -- fresh off roasting Terry Bradshaw at the Super Bowl -- when we asked him about Justin begging for forgiveness for all his d-bag antics.
Let's just say Jeff seems unmoved.
As for what's off limits during Bieber's upcoming Comedy Central Roast ... Ross had a pretty surprising response -- especially considering JB's checkered past.
Watch this ... you can almost see Ross licking his chops.