People come from all over the world for visiting Colosseum and Vatican museum. It means long fila (queue). First of all: visit Colosseum and Imperial ruins in the early morning or late afternoon to avoid the crowds. Second trick: save money booking your ticket on the official site coop culture.it, it costs 12 euros plus a 2 euros booking fee.
Third trick: get Roma Pass for having 2 free entry to 2 museum or archaeological sites, reduced ticket prices to all other museums, free use of the city’s public transport network (Buses, urban trains, underground). With the Roma Pass you can enter in the group entrance. Remember that you can’t avoid queue for sicurity checks. I suggest leave your bags at home. After visit, take a break. Search out Caffè Propaganda, a little corner of Paris near Colosseum. Get a cup of tea with french patisserie. Or a Campari Spritz if is aperitivo time (bar buffet).