Re: anyway of connecting stereo to e kit and hear both through headphones?
wait, wait, wait
why not just do the opposite.
Take a 1/8" cord from your laptops headphone jack and plug it into your 1/8" Mix In jack on the Rolands. It produces a better sound, and you don't need any adapters, just 1/8" plugs.
And then you could take your 1/4" outputs on the Roland and still be able to plug them into a stereo or pa or drum amp.
"When I hear music, I fear no danger. I am invulnerable. I see no foe."- Henry Thoreau