Answer (EN)
2) Will I see you on Sunday? — I don't think so. I'll be in Rome on holiday.
Translation (RU)
2) Я тебя увижу в воскресенье? — Я не думаю. Я буду в Риме на каникулах.
Brief Explanation: 'On' is the correct preposition to use with days of the week. 'Holiday' fits the context of traveling to Rome.