According to the 2019 Hideout brochure, in the "standards and options" chart on page 15, your trailer has a "fully walkable roof".
https://keystone-rv-dealer-app.cdn.p...2pg-lowres.pdf
That said, the TPO membrane can be cut, scuffed or damaged by walking on it, so I'd recommend wearing rubber sole shoes and being extremely careful with what you take "up on the roof" with you. Being cautious about where you step and where you set down a plastic bucket with a sharp ridge on the bottom are essential.
The "old wives tale" about "if there's no ladder it's not walkable" or "if there's a ladder you can walk on the roof" have "qualifiers" that may change the "rules" for some owners. Obviously someone weighing 300+ pounds establishes a different standard of "walkable roof" that's different for someone weighing 150 pounds, just as dragging a pressure washer hose along the edge of the TPO changes the "It's OK to wash your roof with a pressure washer as long as you don't hold the nozzle too close to the membrane"....