I don't think your roll cage is cracked, it did flex though, as most steel structures do to a point.
If you're worried about cracks alongside the weld bead area, I would suggest using a wire wheel to remove the powder coat and look for clear signs of cracked or fatigued metal.
Do not use a grinder, you don't want to take away metal before you determine if any cracks are present.
Welds will seldom crack, unless that weld did not have proper penetration a the time it was welded, or the metal was too brittle, but I don't think that's the case.
I've seen some gnarly maverick roll overs on the web, like Tripp Pullen's Mav. did. The cage was mangled, but none of it's components broke off.
That's the way the cage is designed, to absorb energy by deforming and after a hard hit the cage will be junk.
But I wouldn't worry about a slow roll.
You could also add gussets, to reinforce the affected area, and there's a few ways the cracks could be fixed, I you find any.
I hope this helps.
