Roo is meant for reading Excel files only. I would recommend the axlsx gem.
It can be used in pure ruby as follows
require 'axslx'
package = Axlsx::Package.new
workbook = package.workbook
workbook.add_worksheet(name: 'Some Sheet Name') do |sheet|
sheet.add_row ["Header 1", "Header 2", "Header 3"]
sheet.add_row ["Data 1", "Data 2", "Data 3"]
end
package.serialize('./test.xlsx')
This will create a spreadsheet that looks like
--------------------------------
| Header 1 | Header 2 | Header 3 |
--------------------------------
| Data 1 | Data 2 | Data 3 |
axlsx
offers pretty much everything you can do in excel including styling and conditional styling. Hope this helps you out.