Is it possible to bake vray materials so that I could use them for example game contexts, where all I need is a bitmap per input (color, roughness etc)?
Sometimes the materials in the Vray material library or Cosmos have a longer tree than just one tx-file.
And talking about tx-files - I would benefit from converting them into PNG or JPG for that purpose.
How can I do that baking?
Not sure if I understand correctly. You seem to be talking about regular element baking, which is possible. Go to Rendering > Bake to Texture, and choose from the listed elements (color - VRayDiffuseFilterMap, roughness - inverted VRayMtlReflectGlossinessBake, etc.).
If you wish to bake the texture tree of the VRayMtls itself, you can do that by right-clicking the last texture node (the one that goes in the designated slot) and using Render Map.
What do you mean? Benefit in which way?
As Aleks said, you can RCM on any map in the compact material editor and render it to the resolution you prefer.
Some things will work better than others (bitmaps Vs. noises), and some maps won’t work at all (any of the view-dependent ones, like falloffs).
Tx would be the most memory efficient, and the one with the best filtering, but it’s unknown to me in its use in realtime: it could simply prove too slow for that application.
You’re likely better off baking to PNG/EXR and then re-converting to whatever is best suited for your specific engine (some DX format, perhaps?).