Any-sided multiple dice, multiple rolls

multi-dice.rb

class Dice

  def self.roll( dice = [ "1d6" ], rolls = 1 )
    output = "---\n"

    rolls.times do |roll|
      outcome = []
      dice.each do |die|
        number_of_dice = die.split('d')[0].to_i
        sides = die.split('d')[1].to_i

        number_of_dice.times { outcome << (rand(sides) + 1) }
      end
      output += "Roll \##{roll}: " + outcome.join(" ") + "\n"
    end
    output += "---\n"

    return output
  end

end

puts Dice.roll(["2d6"], 3)
puts Dice.roll(["2d6", "3d4"], 3)