Roland tanks a Trainwreck (indirectly)
|“||Before Roland could say what he thought, Blaine the Mono crashed to a final bitter halt. All four of them were thrown violently up the Barony Coach's central aisle, Oy in Jake's arms and barking. The cabin's front wall buckled and Roland struck it shoulder-first. Even with the padding (the wall was carpeted and, from the feel, undercoated with some resilient stuff), the blow was hard enough to numb him.||„|
|~ Wizard and Glass, page 60|
So, as you can see above, the train crashes and Roland gets slammed into a wall. Said train, according to King's original request that never got traction, has a top speed of well over 800 Miles Per Hour. Of course, it was slowing down prior to the crash, so, just using 800 Miles Per Hour, or, for our purposes, 357.633333333333 Meters Per Second, should be good.
Now that we have speed, to get KE, we'd need to find the weight of Roland. Now, he's described as a Tall, Athletic man, and, due to that, I'll take the assumption that he is 6 Feet Tall with a BMI of about 24.4, or 180 Pounds, or, 81.6466 Kilograms.
So, divide that by half and square 356.633 repeating Meters per second, and the results are...
5221365.4326392124890403177777823137 Joules, 0.00124793628887 Tons of TnT, Wall Level, I'm not sure if it's a + or not, but, it's a lot more then baseline I tell you what.
Roland keeps his grip on a boy in what is basically a hurricane
|“|| He began running again, aware that now he was doing so in absurd leaps, like an astronaut running on the surface of the moon in a science fiction movie. One leap...two...three...
But on the third one he didn't come down. He was blown straight forward with Oy cradled in his arms. There was a gutteral, garumphing explosion as one of the old houses gave in to the wind and went flying southeast in a hail of shrapnel. He saw a flight of stairs, the crude plank banister still attacked, spinning up toward the racing clouds. We'll be next he thought, and then a hand, minus two fingers but still strong, gripped him above the elbow.
Roland turned him toward the door. For a moment the issue was in doubt as the wind bullied them away from safety. Then Roland lunged forward into the doorway with his remaining fingers sinking deep into Jake's flesh.
|~ The Wind Through the Keyhole, pages 26-27|
Alright, so, in winds strong enough to rip apart housing, Roland with one arm is able to keep his grip on Jake and then eventually pull him into cover.
So, this'll be a Lifting strength calc using F=MA, With the mass of a 14 year old kid and 100 MPH winds, as was mentioned to be good assumptions in the replies to the message with the request.
So, with 100 Pounds, 45.3592 Kilograms, and Acceleration, 44.704 Meters per second^2, we'd get 90647.9851036672 Newtons. That's 9.243522008398860912552255488 Tons, or, in Kilograms...
9243.522008398860912552255488 Kilograms, Class 10 Lifting Strength with one of the Gunslinger's arms.