Kraftwerk tones are fairly easy to reproduce, because they are minimalistic, and enhanced by various effects. There are no particular plugins you would need to purchase in order to accomplish your goal.
Do not get trapped into fancy sound creation, and learn to create melodies in the Kraftwerk tradition, i.e. simple and emotional. Apply a certain machine “drive” to melodies and arpeggiators, i.e. not groovy or funky. Drums need to follow this template too. The point is to keep it melodic and grinding in a robotic flow.
Since Robin was kind enough to include a link about them, you can see that they have used so many different machines throughout their time, although simple machines are prevalent.
You can use HALion 5 by Steinberg, which is both a sampler (with some very advanced features) and a synthesizer in one. Go for a vocoder like Matrix by VirSyn, or Lector by Waldorf. I own and use both of those vocoders and they work great. Best of all, the three are 64-bit and VST3!