Theory: Rogueport's Location

Abstract
Rogueport, and the surrounding areas (Petal Meadows, Boggly Woods, the Waffle Kingdom, etc.) are around the area covered by the red box shown in the image (north of the Cascade Kingdom, east of the Mushroom Kingdom, and west of the continent that resembles a bird.)

Arguments

 * Argument 1: Boats appear to arrive from the west when going from Rogueport to the Mushroom Kingdom. Likewise, they face westward when returning to the Mushroom Kingdom.


 * Argument 2: A Yoshi egg is brought to Glitzville from a location south of Glitzville. This egg likely came from an island in or around the Cascade Kingdom.


 * Argument 3: Species indigenous to the Mushroom Continent, (Goombas, Toads, Koopa Troopas, etc.) are common in Rogueport and the surrounding areas.


 * Argument 4: what appear to be Tostarenan Skulls can be seen around the Rogueport area, much like the ones seen on Yoshi’s Island and in the Sand Kingdom, which are both nearby according to this map

Clarified maps
These maps clarify the locations in PipMcGee's High Consensus Theory. By Jupiter Red.