I live around the corner from severn street, i do not know if the house were tied to Rolls Royce i do not think so, they are quite nice semis and terreced houses and would have been quite nice at the turn of the century, what was your rellies name, i have 2 employee record books of workers at rolls royce from the 1920-50 period listing there rate of pay address, d.o.b, war service etc. Severn street was originally called Curzon Street, but just after the turn of the century Alvaston was incorparated into the city of Derby and the name was changed to avoid confusion with a curzon street in Derby town centre. on my 1905 map their are no Houses built yet so in 1910 i would guess the houses were fairly new.
regards Gary