Here are the festivals and events that happen each June in Rome. Note that June 2, Republic Day, is a national holiday, so many businesses, including museums and restaurants, will be closed.
June is the start of summer season so be on the lookout for outdoor concerts held in public squares, church courtyards, and ancient monuments.
June 2 - Republic Day (Festa della Repubblica). This big national holiday is akin to Independence Days in other countries. It commemorates Italy becoming a Republic in 1946 following the end of World War II. A huge parade is held on the Via dei Fori Imperiali.
Rose Garden - The city's Rose Garden is open to the public during May and June, usually through about June 23 or 24. Via di Valle Murcia 6, near the Circus Maximus.
Early- to mid-June - Corpus Domini. Exactly 60 days after Easter, Catholics celebrate Corpus Domini, which honors the Holy Eucharist. In Rome, this feast day is typically celebrated with mass at the cathedral of San Giovanni in Laterano followed by a procession to Santa Maria Maggiore. Many towns hold an infiorata for Corpus Domini, creating carpets with designs made of flower petals in front of the church and along the streets. South of Rome, Genzano is a good town for flower petal carpets, or head north to the town of Bolsena on Lake Bolsena.
June 23-24 - Feast of Saint John (San Giovanni). This feast is celebrated in the vast piazza that it in front of the church of San Giovanni in Laterano, Rome's cathedral. Traditionally the celebration includes meals of snails (lumache) and suckling pig, concerts and fireworks.
June 29 - Saints Peter and Paul Day. Two of Catholicism's most important saints are celebrated on this religious holiday with special masses at Saint Peter's Basilica at the Vatican and San Paolo Fuori Le Mura.