Do I need to pay deflect costs when playing Switcheroo?

Yes, you must pay the Deflect cost when casting Switcheroo on a unit with Deflect.

According to the official ruling:

• Yes, you must pay for Deflect when casting Switcheroo on a unit with Deflect, because Switcheroo is a spell and you are choosing (targeting) the unit with Deflect.
• Nuance: This only applies if the unit with Deflect is controlled by an opponent.

Because Deflect is a mandatory additional cost (Rule 735.1.d), it must be paid when the spell is placed on the chain, before the spell resolves.