I got stuck last night how to manage power rate of resistor because I couldn’t find the exact resistor which have the power rate from a circuit analysis.
The power rating of the combination will be the rating of one resistor times the number of resistors for a either a series or parallel circuit. Of course the resistance of the combination will be N*R for the series circuit, and R/N for the parallel circuit. If the series-parallel circuit has the same number of resistors in each series or parallel subbranch, then the total rating will also be the number of resistors times the individual rating
To follow up, (now that I understand your question a bit better), I just would not apply that approach. It is best practice to compute your expected power dissipation per device and then derate each device.
Using N identical resistances of value R rated at P power rating. Rt = total resistance, Pt = total power dissipation
parallel: Rt = R / N , Pt = N x P
series: Rt = N x R , Pt = N x P
combo: Rt depends on arrangement, Pt = N x P