रस्

• (Vedic) IPA^(key): /ɾɐs/
• (Classical Sanskrit) IPA^(key): /ɾɐs̪/

Uncertain. Perhaps, with रास् (rās), from an extension of Proto-Indo-European *rey- (“to roar”). (Can this⁽⁺⁾ etymology be sourced?)

रस् • (ras)

1. to roar, yell, cry, sound, reverberate
2. to praise

• Monier Williams (1899), “रस् 1.ras”, in A Sanskrit–English Dictionary, […], new edition, Oxford: At the Clarendon Press, →OCLC, page 869, column 2.
• William Dwight Whitney (1885), The Roots, Verb-forms, and Primary Derivatives of the Sanskrit Language, Leipzig: Breitkopf and Härtel, page 137

• Hellwig, Oliver (2010–2026), “ras”, in DCS - The Digital Corpus of Sanskrit, Berlin, Germany.
• Mayrhofer, Manfred (1996), “RAS”, in Etymologisches Wörterbuch des Altindoarischen [Etymological Dictionary of Old Indo-Aryan]‎^[1] (in German), volume 2, Heidelberg: Carl Winter Universitätsverlag, page 441

Denominative root from रस (rása).

रस् • (ras)

1. to taste, relish
   • c. 700 BCE, Śatapatha Brāhmaṇa
   • c. 400 BCE, Mahābhārata
2. to feel, perceive, be sensible of (Sāh.)
3. to love (Dhātup.)

• Monier Williams (1899), “रस् 2.ras”, in A Sanskrit–English Dictionary, […], new edition, Oxford: At the Clarendon Press, →OCLC, page 869, column 2.