I agree with H. The plugs look good. I don't see any lean coloring.
Rough idle at a cold start with a carb'd engine is not uncommon.
A cold start rough idle, that goes away immediately at warm up, is almost always caused by the air fuel mixture.
Ambient air temperature and air density - Relative Humidity and Elevation (barometric pressure) can also significantly affect AFR.
Why does the carb NOT have a choke or an AAP?