Why should Brahman the Absolute love to be called by three, and only three, different names? Do they Really love to be called so? Are Brahma, Vishnu & Mahesh names of the same God? Why should God the Almighty need, like silly, benighted humans, weapons (Brahmastra, Pashupatastra, etc.), armours (Shiva-Kavacha), shields (Srivatsa), etc.? Does RgVeda Really support the view that Brahma, Vishnu, and Mahesh are names of the same entity?
The concept of Trimūrti in specific-explicit reference to Brahmā, Viṣṇu, & Maheśa (Śhiva) is not stated explicitly in the Ṛg-Veda, i.e., the three deities which are discussed together as an "equivalent-triad" in detail, in the Paurāṇika-literature, are not discussed together as the tri-devas of the Trimūrti godhead, in any major Ṛg-Vedic Literature and definitely not in the saṃhitās.
So basically, the question:
“Does Ṛg-Veda support the view that Brahmā, Viṣṇu, & Maheśa (Śhiva), are names of the same Brahman - the Absolute?”
This question finds no ground to even have a proper answer.
However, in its broadest spirit, the Ṛg-Vedic Saṃhitā gives even a larger Umbrella of what constitutes the Supreme & Absolute Brahman as follows:
इन्द्रं॑ मि॒त्रं वरु॑णम॒ग्निमा॑हु॒रथो॑ दि॒व्यः स सु॑प॒र्णो ग॒रुत्मा॑न् ।
एकं॒ सद्विप्रा॑ बहु॒धा व॑दन्त्य॒ग्निं य॒मं मा॑त॒रिश्वा॑नमाहुः ॥४६॥
índram mitrám váruṇam agním āhuḥ átho␣íti divyáḥ sáḥ su-parṇáḥ garútmān |
ékam sát víprāḥ bahudhā vadanti agním yamám mātaríśvānam āhuḥ || 46 ||
Indra, Mitra, Varuṇa, Agni, they say about, Even then he is the divine Suparna, the Garutmān. One is the reality, which inspired-wise ones speak of variously, They speak about Agni, Yama, Mātariśvan.
Śhrī Aurobindo Ghose gives the following notes on the same verse:
It is the one Existent to whom the seers give different names, Indra, Matarishwan, Agni, etc.
[4. Source № 208. July 1915]
The Existent is One, but the sages express It variously; they say Indra, Varuna, Mitra, Agni; they call It Agni, Yama, Matarishwan.
[5. Source № 261. January 1915]
Therefore, the Ṛg-Veda very much supports the idea that the Supreme Brahman manifests in myriad forms, which even if not explicitly stated, also represents the Trimūrti deities - Brahmā, Viṣṇu, & Maheśa (Śhiva).
For a traditional interpretation of the Verse by Yāskācārya & Sāyaṇācārya see this QnA. The basic gist of the interpretation even though then, will still remain the same as explained above.
Not only Brahma, Vishnu, Shiva, all the deities in vedas are names of same Parabrahma.
Rigveda 1:164:46. They call him Indra, Mitra, Varuna, Agni, and he is heavenly nobly-winged Garutman. To what is One, sages give many a title they call it Agni, Yama, Matarisvan.
The same thing is said in other vedas.
Yajurveda 32:1. AGNI is That; the Sun is That; Vâyu and Chandramâs are That. The Bright is That; Brahma is That, those Waters, that Prajâpati.
Atharvaveda 9:10:28. They call him Indra, Mitra, Varuna, Agni; and he is heavenly nobly-winged Garutmān. That which is One bards call by many a title: they call It Agni, Yama, Mātariswan.
This one is from Upanishads;
Shwetashwara Upanishad IV-2: That Itself is the fire, That is the sun, That is the air, That is the moon, That is also the starry firmament, That is the Brahman, That is the waters, That is Prajapati.
Kavialya Upanishad 8. He is Brahma, he is Siva, he is Indra. He is the imperishable, supreme self illumined Lord. He alone is Vishnu. He is the life giving breath. He is time, he is fire, and also the moon.