Hi, do people use scrubbing services, when under DDoS attack, by having the scrubbing service announce the attacked IP prefix(es)?

If so, and you have a ROA for these prefixes, do you authorize the scrubbing AS (by issuing ROA or otherwise), and if so, do you do it in advance or only when you need the scrubbing service to announce your prefix? 

To clarify: we have a possible method to allow such `emergency ROAs' but I'm not convinced if we have a solution to a real problem - or if we just found a cute crypto solution and will end up writing it for a non-real problem. I prefer not to waste our time on presenting cute solutions to non-real problems :) 

So thanks for your help! Use your judgement if to respond on list or off list. 

Many thanks, Amir