"... but it appears NaN in the cells of the Role column."
Sounds like the Role column is an empty cell array or a numeric column. Table columns but contain the same type of data and cannot contain mixed classes. You can use a cell array to enter mixed data types if needed.
Players = table(["abc";"dcd";"cdf"], cell(3,1),'VariableNames',{'Name','Role'})
Players.Role{1} = 'Cricketer';
If the entire column should be strings, you can convert the cell array to a string array,
Players.Role = repmat("Cricketer", size(Players.Name))
or you can set the initial values of "Role" as a string array rather than a cell array,
Players = table(["abc";"dcd";"cdf"], ["";"";""],'VariableNames',{'Name','Role'})
Players.Role(:) = "Cricketer";
