I would call the ER ASAP.....
Rivoltril (clonazepam) is a benzodiazapine - so the short answer to if you can die from an overdose of it is 'yes'.
How much will depend on your metabolism, weight, overall general health, how tolerant you are to benzos - amongst other things.
Symptoms of overdosage of Rivotril can be drowsiness, confusion, reduced reflexes depressed respiration rate and coma.
Not trying to be dramatic but if you really believe you have taken enough to overdose, you need to seek urgent medical attention - benzo's shouldn't be messed around with.
How much did you have and how long ago? Is anyone at home? It's hard to assess your situation with the little info in your post.
Good luck.