Is a number written in roman numerals a roman numeral, or is each of its digits a roman numeral?

The Oxford English Dictionary entry indicates that any single digit or any number is called a 'numeral'.

For example, one of the entries :

1935 J. O'Hara Appointment in Samarra (U.K. ed.) vii. 197 The little clock had no numerals but only squares of metal where the numerals were supposed to be,

expresses the numbers one to twelve as 'numerals'. If the numbers were in Roman style, then there would be two digits for some of the 'numerals'.

Where individual digits are in view the term 'numeral characters' is used :

1728 E. Chambers Cycl. at Character. Numeral Characters, are those used to express Numbers.

1840 Penny Cycl. XVI. 366/2 Distinct numeral characters are found to have existed..among the Chinese, Indians, and Arabs.

Each digit (I, V, X etc.) is a 'roman numeral'. The entire number would be described as 'expressed in roman numerals'.

I notice, however, that Unicode characters (Ⅷ, ⅺ, Ⅿ etc.) representing entire numbers are described as a 'numeral'.