What do the roman numerals in a cation's name indicate?
how many valence electrons in the atom
the cation's ability to become an anion
the positive charge on the cation
how many compounds the cation can form

Option (c) is the correct answer.

Explanation:

When an element gain electrons then it acquires a negative charge. For example,

Whereas when an element loses electrons then it acquires a positive charge.

For example,

The atom can also be written using roman numerals as Fe(II).

Therefore, we can conclude that roman numerals in a cation's name indicate the positive charge on the cation.