Shift Click Mapping could be the answer for the Roofes,
sadly all Pictures in this awesome Tutorial are gone. I linked it dozens of times in the last Years.
Maybe it is still helpful in this case.
Shift+Click Mapping There's a lot of game designers out there that don't know how to use many of the built in tools of RPG Maker. The visuals of a game is arguably the gateway to the players free time. Screenshots often dictate whether a game will be played or glanced over. Often times I see...
forums.rpgmakerweb.com
Edit: The second Problem with the Vendor, is a little tricky...
Edit2: If you use an Event for the Shop Maptile infront of the Vendor NPC,
he can be displayed behind it, while the player is displayed infront.
Therfor it needs to have Priority: Same as Character.
If it still not work, than:
If i remember correctly higher Event Ids would be shown over lower ones.
If it is needed to Place 2 Events on the same Maptile, which i hope is not needed, you can teleport
one everytime the Player enters that Map.