It's really not going to be a mystery why this workout was named "The Steamroller" by the time you're done. Pavement, meet roster.
While 20 reps per exercise is at the outer limits of a good idea in workout program design, for this workout, it's exactly what a rucker might need. For an Intermediate level athlete, it's a good idea to get high rep workouts in a few times per PATHFINDER Class cycle. This is a great place to apply the 80/20 rule - 80% of your workouts should be well within your grasp or just slightly above your level. 20% of them should leave you on the ground.
Ideally, you should be working with enough weight that anything over 14 reps feels dodgy, but a 35-40lb ruck is light enough to test those boundaries with this range.
You should be wearing a ruck for the push-ups, mountain climbers, and salute plank.
You should be holding your ruck for the jump squats, rotational lunges, and you may hold your ruck with straight arms over your head for the reverse crunches.
If you're at a more advanced level of fitness, go for 4, or even 5, rounds of this workout.