We can directly type Roman Numbers and Capital Roman Numbers without using any package.

  • Roman Numbers command: \romannumeral + num
  • Capital Roman Numbers command: \uppercase\expandafter{\romannumeral + num}

For example 

1
2
3
4
5
6
7
8
9
Some Roman Numbers: 
\romannumeral1, 
\romannumeral3, 
\romannumeral6.

Some Capital Roman Numbers: 
\uppercase\expandafter{\romannumeral1}, 
\uppercase\expandafter{\romannumeral3}, 
\uppercase\expandafter{\romannumeral6}.

The result