I believe in German-speaking countries the X-ray machine is called Röntgen? E.g. in a hospital you will have directions for "Röntgen".

We call it "Röntgenstrahlung" (X-rays), "Röntgengerät" (X-ray machine), "Röntgenaufnahme" (X-ray picture). We even made a verb out of it, even though that's probably colloquial: "Wir müssen Ihr Bein röntgen" (we need to X-ray your leg).

Rentgen is a noun in Czech meaning 1. the machine, 2. the picture, the root of an adjective (rentgenový), Amd the root of a verb (rentgenovat).

In lots of languages, both are used (thought X-rays becomes more and more common).

a lot of languages call it Roentgen rays or similar

At my work maybe 10 years ago, we had a little trivia competition on a fun day, about 25 people taking part - one of the questions was "who discovered the X-ray?", and all 7 of the eastern Europeans got the correct answer, but none of the Americans, Indians, or Asians in the group got it right (except for me, but I'm special).