That's a Torrington full-complement (crowded needles, no cage separators), which has a suitable outer race (as shown) but uses the original cam journal as the inner race.
The advantage compared to a caged bearing: more rollers of the same size.
This is not always safe, the journal surface hardness may not survive.
The needles don't like being turned very fast (even with the cam at half-speed), since each needle is rotating opposite to it's neighbor on both sides.