Don't be mad at your cat. he saw an opportunity and he took it.He
doesn't know he's diabetic, or that he has to watch what he eats.

Don't panic. One blood sugar spike in a controlled cat isn't going to do
any damage. It's when things go on for days on end that you can have
issues. Get him back on his regular feeding schedule and he should be
fine.
I'm also guessing you do not have a blood glucos monitor. Incidents ike
these are one of the many good reasons to have a meter, because you
could check his blood sugar and see just how much the roll affected him.
If you do get a monitor, the best one I've found is the One Touch Ultra.
Another thing you might consider, but only if you get a monitor and get
good at checking blood sugar, is to think about switching to Wellness
*canned* food as it is lower in carbs than the DM and has much better
ingredients. I have a client who had to take her diabetic cat off of dry
food (to my relief!) as the grains in it were making him throw up, He
was switched to Eukanuba Low Residue canned and his insulin dose went
down from 6 units twice a day to 3.5.
I asked her if we could experiment with Wellness as I was caring for him
for a week and could monitor his blood sugar closely. She agreed and he
is now down to 1.5 units twice a day and has a variety of flavors to eat
(the carb content is similar in all flavors) so he doesn't get bored
with having to eat the exact same food day in and day out.
One caution is to make sure that any cans you buy don't have GW in the
code. Those cans contain rice, but aren't labeled as such, and
apparently were an experimental batch that was not supposed to be
shipped for sale at stores. I don't now how much that would change the
carb content, but I'd raher stick with the cans that I know are grain
free. HTH.

Megan