Crystal Roaming Johto
Less a place than a chase: once the beasts wake at the Burned Tower, Raikou and Entei tear across Johto's routes and flee the instant you corner them.
Roaming Johto is in Johto. In the story it comes after Route 39 and before Olivine City.
ROAMING JOHTO MAP
Pokemon Encounters
In Crystal only two of the three beasts wander loose. Raikou and Entei stalk Johto at level 40 and flee the moment the battle opens, so come with something that pins them in place and plenty of Ultra Balls. Suicune is not among them here, since it waits at Tin Tower instead.
Entei
Roaming Johto Guide
Suicune is no longer one of them. Crystal pulls it out of the roaming trio for a fixed catch at the Tin Tower, which leaves just Raikou and Entei wandering the routes at level 40. Both still bolt on the first turn, so bring Mean Look to trap one.