OK. You want to know the wattage rating required for the resistor on the ADJ terminal of the LTM8021.
Understanding is required. That resistor does NOT have half an amp flowing through it. Looking at the datasheet, that is merely a very low current meant to set the output voltage. I'm not quite sure what current will be there, but if we say 0.8V/100k (page 6, resistor in the block diagram between Vout and ADJ) = 8uA, we can guess that we have a current somewhere in that range through that external resistor.
Power is also equal to Current Squared times Resistance.
19.1k x (8uA^2) = 1.222uW
So... I don't think there is a resistor made with a low enough power rating to be a problem here.
You see, it is important to understand the question before giving an answer, and before accepting an answer.