It's a german requirement (10 years from manufacture).
This does not apply to the UK, although some competitive events may have a similar requirement, notably those run by the ISSF.
Here's the page from the Weihrauch manuals which will cover the same ground as that in the Rohm manual.
So unless you plan to use the Rohm outside of the UK, or enter ISSF events then there is no need to have it tested, unless you believe it to be damaged etc.