Romans didn't build obelisks. Obelisks were built by the Ancient Egyptians.

obelisks were build to honor the gods .

Egyptians back then carved hieroglyphics on obelisks.

Obeslisks, usually a four sided monument ending in a pyramid shaped top, constructed by a monolith [ancient times] can be found in Middle East, Egypt, Rome [Roman Empire] and Latin America. Currently obelisks can be founf in USA and major European capitals ans were constructed in the past 300 years.

Several Roman emperors had obelisks brought to Rome from Egypt.

Augustus brought two obelisks, the Flaminian Obelisk and Solar Obelisk, from Heliopolis in 10 BC

Caligula brought the the Vatican Obelisk in 40 AD. It had been brought from Karnak to Alexandria of Egypt by Augustus in 30-28 BC

The Piazza Navona Obelisk was brought from Sais by Domitian

The Pincian Obelisk was brought by Hadrian

The Minervan pair of obelisks were brought by Diocletian

The Lateranense Obelisk was brought from Amun by Constantius II

The Matteian Obelisk was unearthed in the 14th century, the Macutean Obelisk in 1373 Dogali Obelisk in 1833. We do not know who brought them to Rome