Adjective meaning "of the same resolution and extent"

The reason you are struggling to find a better word or shorter phrase for it is probably because one doesn't exist! I think "rasters of the same extent and resolution" is pretty short, clear, and unambiguous to most people who deal with raster data. Other suggestions, like "coincident" or "co-registered" don't (to me) imply the perfect match of one raster's cells with the other.

How about we use "SEAR" (Same Extent And Resolution) as an abbreviation? Sample usage:

The DEM and the NDVI are SEAR rasters so we can add them in the raster calculator.

It probably won't catch on...

Two rasters could be same extent and resolution but different coordinate reference systems and so not line up perfectly. If you want to specify all those things equal then those would be SECAR (Same Extent, CRS, And Resolution). Maybe.

How about congruent ?

co-referential

co-rectified

even concordant -- see the geological and medical uses. A lot of technical terms are appropriations based on the original Latin or Greek roots, eg: cursor (related to courier, etc).