RSS types are defined as filters within the :'rss.out' group. To add a new type, you can create a file rss/types.rb in your bot directory (typically ~/.rbot) and define a filter using a syntax such as the following:

rss_type :forum do |s|
  line1 = "%{handle}%{date}%{author} ha scritto su %{title} @ %{link}"
  make_stream(line1, nil, s,
              :handle_wrap => ["#{Reverse}[", "]#{Reverse} "],
              :author_wrap => Bold,
              :title_wrap => [Irc.color(:green), NormalText])
end

This (re)defines the :forum type to have italian text, wrapping the handle in square brackets, with a reverse font, bolding the author and writing the title in green. Example output:

[forum] ivan ha scritto su TeX e LaTeX :: RE: Note in Beamer: per gli esperti @ http://www.guit.sssup.it/phpBB2/viewtopic.php?p=30633#30633

If you want to have a two-line output, just define a line2 with the content of the second line, and put it instead of nil as the second parameter to make_stream()