This poem is commonly interpreted as being spoken by a narrator shocked at how coarse life in the kitchen can coexist in the same house with death (the corpse of an old woman) in the parlor. Then he concludes that the grossness of life (preparing food, including ice cream, for the wake) is all there is: death is final and all we can do is choose to live life with all its imperfections, to enjoy its delights however transient rather than dwell in illusion.
Note that the poem is believed to have been written in Key West and draws on the African-American southern cultural custom of serving ice cream at wakes: it may seem grotesque to northern white audiences but is not so in the context. Similarly the references to a cigar-roller should be taken in the Florida context, where it was a common occupation.
Vendler's prose summary is availalbe at: http://www.english.illinois.edu/maps/poets/s_z/stevens/emperor.htm