A:AnswerI was connecting a DVI monitor to an HDMI input of a projector. It worked great. Im not sure what you are trying to do with three monitors. Can you give me more details.
A:AnswerIf the Dell monitor is DVI then you don't need this. Just use a Mini Display Port to DVI Adapter (https://www.bestbuy.com/site/insignia-mini-displayport-to-dvi-adapter-white/5813102.p?skuId=5813102).
A:AnswerRoku has an HDMI port. What port does your TV have? If it is HDMI, all you need is an HDMI cable. If you TV does not, you will need the proper powered adapter.
A:AnswerThe resolution on your computer does not match your TV. You need to adjust your resolution on the computer to match your TV. Do this with a spare monitor and the connect back to your TV once changed.
A:AnswerWill depend on which MacBook Pro you have, but this isn't what you are looking for.
My MacBook Pro needed a Mini Display Port to HDMI (https://www.bestbuy.com/site/insignia-mini-displayport-to-hdmi-adapter-white/5813015.p?skuId=5813015), but the newer ones need USB-C to HDMI (https://www.bestbuy.com/site/insignia-usb-type-c-to-hdmi-multiport-adapter-with-power-delivery-white/5577934.p?skuId=5577934).