Roanu originated from a low-pressure area that formed south of Sri Lanka, which gradually drifted north and intensified into a cyclonic storm on 19 May.

Roanu also brought torrential rainfall to the Indian states of Tamil Nadu, Andhra Pradesh, Kerala and Odisha as it drifted in a generally northeastward direction, close to the coast.

[2][3] It slowly consolidated as it paralleled the east coast of Sri Lanka, prompting the India Meteorological Department (IMD) to classify it as a depression on 17 May.

[5][6] Simultaneously, the IMD upgraded the storm to a Deep Depression, prompting the issuance of cyclone warnings for the states of Andhra Pradesh and Odisha.

Despite favorable outflow and warm sea surface temperatures (SSTs) reaching 31 °C (88 °F), its proximity to land and moderate vertical wind shear kept the storm from intensifying rapidly.

[9] The diurnal temperature variation over land and the persistent wind shear began to affect the deep convection obscuring the low-level circulation center (LLCC).

However, the wind shear soon decreased,[10] and the storm reestablished deep convection over and around the LLCC, forming a central dense overcast in a period of 6 hours.

[11] As a result, Roanu re-intensified as it accelerated east-northeastwards towards the coast of Bangladesh,[12] and reached its peak intensity with winds of 85 km/h (55 mph) and a minimum central pressure of 983 hPa (mbar; 29.03 inHg).

[19] Later, The National Building Research Organisation (NBRO) issued landslide warning in the districts of Badulla, Monaragala, Kandy, Ratnapura, Kurunegala, Nuwara Eliya, Kegalle and Matale.

The Minister Of Disaster Management, Defense Secretary, Tri Forces' Commanders and the Inspector General Of Police were instructed to undertake the operation.

[21] Sri Lankan Disaster Management Centre (DMC) issued a flood alert on 16 May as the low-pressure area brought heavy rains to the country.

[22] The depression brought torrential rains to Sri Lanka, causing flash flooding and landslides, resulting in 37 deaths.

[28] The IMD put the states of Andhra Pradesh and Odisha on an orange alert (the second highest level of emergency in India) on 19 May.

[29] Chief Minister of Andhra Pradesh N. Chandrababu Naidu positioned 5 teams, each consisting of 100 personnel, in Krishna, East Godavari and Visakhapatnam districts.

[18] Rescue operations began soon after the storm, on 18 May, with Sri Lankan military personnel searching for missing people in rural areas.

[42] On 20 May, the Indian Navy Southern Naval Command sent its ships INS Sunayna and HMIS Sutlej with relief material to the capital city, Colombo.