I haven't taken roaccutane myself, but I know it can be quite a difficult drug to take. It essentially dehydrates you; you have to go on a pregnancy protection programme/ take contraception because it causes severe birth defects if taken when pregnant. It's quite a controversial drug, but I have seen some amazing effects.
There are lots of suggestions that it can cause type 1 - although theses are just internet theories and are likely unfounded.
The patient information leaflet does however say it can cause high blood sugar and in rare cases cause diabetes (I'm assuming type 2). So it could well make you a bit insulin resistant.
Ask your dermatologist and dsn about whether roaccutane is contraindicated for type 1s.