User has only read only access on COA, Payment Term, Exchange rates

Summary:

User has a requirement that his employee Mr. X will have the read only access of particular areas i.e. Chart of accounts, payment terms, receivable payment terms, exchange rates. For this I have created custom roles and applied it to that user although these custom roles have applied successfully and now the user has the access of that particular areas only but the issue that arises is that user doesn't only have the access of that particular area but is also able to update on it.

Kindly assist regarding this that the user has only read only access.