Just yesterday a new feature became available in RubyMine: the Rails console.
Now you can use the console for whatever you got used to.
Open it with Run | Run Rails console…, select the environment you want to use
and do what you need:
The console provides syntax highlighting, commands history using Up/Down arrow buttons,
And you can configure the console colors in Settings | Editor | Colors & Fonts | Ruby Console.
The feature will be available in the nearest public build of RubyMine.