Node IDs are not stable across project runs. Instead, you need to rely on something else such as an inheritance check (if node is KinematicBody2D), a method-presence check (if node.has_method("roll_over")) or a node name check (if node.name == "SomeNode").
The is approach is recommended most of the time, as it is the strongest in terms of safety. Node names should only be used as a last resort, as they will not work if the node is duplicated at the same level. This is because Godot does not allow several nodes to have the same name at the same level in the scene tree.