Calculating RC snubber network current?
The SW1 pin will be Vin + the transient. For 3.3V it doesn't get much more than 4V. So maybe 1V through the cap (momentarily for a few ns, we'll figure the transient square instead of peaky for calcs sake and lasts 10ns with a height of 1V only the AC will go through the cap and reach the resistor).
I don't think I'd worry about the power at all. That pulse is small, way less than 10ns. \$1V^2*2Ω = 2W\$ and \$2W*10ns/1s= 20nW \$ Even with a pulse rate of 1MHz this would be 20nW*1e6 or 20mW, any resistor could handle that and that is worst case upper-bound.
If your really worried about it simulate it, it's really easy with lt spice (if they have the model and they do for 90% of converters, or use LT power cad to generate the spice file)