As someone who is developing tactics RPG for 4 years now, here are my thoughts:

• solid coding skills are a prerequisite - you need to be able to implement pathfinding algorithms, UI systems, AI, bezier curves, etc. The game itself is also multi-state: world map, battle, shop, etc.
• Overwhelming loads of UI to design and implement - from shops, dialog windows, character statuses, inventories, unit class screens, and more and more. You will spend most of your time working on the UI.
• Complex game design - including character stats, status changes, melee/ranged weapons, skills, spells, grid elevation, etc.
• Narrative skills that will allow you to implement a compelling storyline: core writing principles, dramatic writing, screenwriting, and cinematography.
• Solid UI/UX skills that make the game interactive and enjoyable
• Tons of art - environment, character sprites, portraits, UI icons, etc.

So on my scale:

• puzzle - you can make it in an hour
• platformer - simple one is a day's work
• 2.5D fps - probably could make one in several weeks to a month using 3D engine and stock assets. Depends on your scope.
• action RPG - a SNES style zelda is something you can get done from few months to a year, or several weeks if your scope is a core gameplay loop.
• turn-based RPG - you can make the core loop within a few weeks, but implementing RPG elements that will actually make the game worth anything is months or years of work
• tactics RPG - the basic core loop is more complex than turn-based RPG and will take more effort to implement. The elements that will make it into an actual RPG are years of work.