Rather than write your own slides, use this resource to generate Roman numerals for class questioning. Set the range bands and then generate as many as you want. The second button gives helpful hints to assist learning such as the decimal equivalents and the places where subtraction needs to be used to work out the Roman numeral (the red bands).
The bottom button gives the answer. Simple to use with either an IWB or with a tablet for small group work.
Go to Roman Numeral Flashcards.
The Roman Numerals Complete game is a good accompaniment to this resource providing an opportunity for children to practise within the same number ranges.