Many illusion spells succeed automatically at first, but have a check that can be made to see through them (disguise self and silent image do for example).
Other than attack rolls, the caster does not need to roll for spell effectiveness (but if a spell is being used in a social situation, their may be a related social skill roll.
Illusions generally have a perception/investigation check if they get interacted with, failure meaning the power of the magic caused the person not to notice things passing through other things. Otherwise, they are effectively perfect at what they do, though they may fail because of what they don't do. Silent image will likely fail if the image should generate sound and doesn't. Disguise self is pretty good if you're just trying to not be yourself, but if you're trying to be someone else, you'll need to roll since it only changes your appearance.
As for comprehend languages, it just works, no roll necessary.
To my understanding, if a spell's description doesn't state "make an attack" or "saving throw" then it just automatically hits or does its thing.
An example being Disguise self, Silent image, & comprehend languages.
Or is it common for the dm to ask me to roll to see how effective my illusion is
Thanks in advance
Many illusion spells succeed automatically at first, but have a check that can be made to see through them (disguise self and silent image do for example).
Other than attack rolls, the caster does not need to roll for spell effectiveness (but if a spell is being used in a social situation, their may be a related social skill roll.
Illusions generally have a perception/investigation check if they get interacted with, failure meaning the power of the magic caused the person not to notice things passing through other things. Otherwise, they are effectively perfect at what they do, though they may fail because of what they don't do. Silent image will likely fail if the image should generate sound and doesn't. Disguise self is pretty good if you're just trying to not be yourself, but if you're trying to be someone else, you'll need to roll since it only changes your appearance.
As for comprehend languages, it just works, no roll necessary.
Awesome, thanks for the clarification !