Yes, ROENTGEN is a Scrabble word!

Letter values in Scrabble US: R 1, O 1, E 1, N 1, T 1, G 2, E 1, N 1.

Is it a valid word?

ROENTGEN is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
German physicist who discovered x-rays and developed roentgenography (1845-1923)

Also: r, wilhelm konrad roentgen, wilhelm konrad rontgen.