There's more about the role of German scientists and engineers in the Soviet space program in James Harford's biography of Sergei Korolev, "Korolev: How One Man Masterminded the Soviet Drive to Beat America to the Moon".

IIRC, the Soviets kept the Germans separate from the team of Russians working on rocket development, preferring that the two sets work in parallel rather than collaborating. The idea was to encourage the growth of a completely Russian set of aerospace professionals, while having the Germans available to help provide boosts over particularly knotty technical problems until the home team had come up to the desired level of perfomance. The Germans were largely phased out of the program and sent home well before Sputnik.

Anyway, Harford's book is a wonderful read. I'd recommend it unreservedly.