How does DM stack against the RoS? (in General)

Lets say I have a RoS level 1000... I should be protected against a DM effect of up to 400 (40% of 1000).

Now, lets say an opposing character trains DM on 3 minions for an effect of 150 each. The effects will stack up to 450.

However, will my RoS cancel all DM effects because they are all lower than 400... or will there be a DM effect of 50 (i.e. (150*3) - 400) cast on my character?

RoS doesn't cancel out DM completely. I know this because it says so in the Wiki. Beyond that little detail, I know nothing else about what you need to know.

Following up on this message after doing some researching...

The RoS, as far as I can tell, completely nullifies DM up to 40% of its level. At the very least, I do not see any affect on my defensive spells effects.

As far as stacking goes, DM does not stack against the RoS protection.

Here is an example to illustrate:

Lets say I equip a RoS level 1000. This gives me a total protection of 400 against opposing DM effects.

Imagine an opponent has DM trained on 2 minions with respective effects of 500 and 700. When attacking me, The DM's will have respective effects of 100 (i.e. 500-400) and 300 (i.e. 700-400) for a total effect of 400.

If the 2 DM's had stacked, they would have had a total effect of 800 (i.e. 500+700-400).

Now I love my RoS even more.