You don't have to do anything special, it should just be working.
When I have a fresh rails app with this controller:
class FooController < ApplicationController
def index
raise "error"
end
end
and go to http://127.0.0.1:3000/foo/
I am seeing the exception with a stack trace.
You might not see the whole stacktrace in the console log because Rails (since 2.3) filters lines from the stack trace that come from the framework itself.
See config/initializers/backtrace_silencers.rb
in your Rails project