Who are the Adityas, Maruts, Rudras, Aśvins and Vasus?

 According to Śatapathabrāhmaṇa 4.5.7.2, there are 33 Gods + Prajapati.

अष्टौ वसवः | ऎकादश रुद्रा द्वादशादित्या इमॆ ऎव द्यावापृथिवी त्रयस्त्रिंश्यौ त्रयस्त्रिंशद्वै दॆवाः प्रजापतिश्चतुस्त्रिंशस्तदॆनम् प्रजापतिं करॊत्यॆतद्वा अस्त्यॆतद्ध्यमृतं यद्ध्यमृतं तद्ध्यस्त्यॆतदु तद्यन्मर्त्यं स ऎष प्रजापतिः सर्वं वै प्रजापतिस्तदॆनम् प्रजापतिं करॊति तस्मादॆताश्चतुस्त्रिंशद्व्याहृतयॊ भवन्ति प्रायश्चित्तयॊ नाम

aṣṭau vasavaḥ | ekādaśa rudrā dvādaśādityā ime eva dyāvāpṛthivī trayastriṃśyau trayastriṃśadvai devāḥ prajāpatiścatustriṃśastadenam prajāpatiṃ karotyetadvā astyetaddhyamṛtaṃ yaddhyamṛtaṃ taddhyastyetadu tadyanmartyaṃ sa eṣa prajāpatiḥ sarvaṃ vai prajāpatistadenam prajāpatiṃ karoti tasmādetāścatustriṃśadvyāhṛtayo bhavanti prāyaścittayo nāma

There are eight (8) Vasus, eleven (11) Rudras, twelve (12) Adityas; and these two, Heaven and Earth, are the (thirty-second and) thirty-third. And there are thirty-three gods, and Prajapati is the thirty-fourth;—thus he makes him (the sacrificer, or Yajna) to be Prajapati: now that is, for that is immortal, and what is immortal that is. But what is mortal that also is Prajapati; for Prajapati is everything: thus he makes him to be Prajapati, and hence there are these thirty-four utterances, called expiations.

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As per the Rig Veda 2.1, there no separate physical Gods, but different epithets, viz., AGNI, INDRA, VISHNU, Adityas, Rudras, etc, referring to the same BRAHMAN.

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As an extension of this concept, consider the following Riks, which say Mitra and Varuṇa, the Adityas are Rudras and Vasus.

Rig Veda 5.70.3 - Dedicated to Mitra and Varuṇa

पातं नो रुद्रा पायुभिरुत त्रायेथां सुत्रात्रा । तुर्याम दस्यून्तनूभिः ॥
pātaṃ no rudrā pāyubhir uta trāyethāṃ sutrātrā | turyāma dasyūn tanūbhiḥ ||

English translation:

Protect us, Rudras, by your protections, and rescue us, since you are good rescuers.
We in our own persons would overcome the Dasyus.

Rig Veda 7.52.1 - Dedicated to ādityās

आदित्यासो अदितयः स्याम पूर्देवत्रा वसवो मर्त्यत्रा । सनेम मित्रावरुणा सनन्तो भवेम द्यावापृथिवी भवन्तः ॥
ādityāso aditayaḥ syāma pūr devatrā vasavo martyatrā | sanema mitrāvaruṇā sananto bhavema dyāvāpṛthivī bhavantaḥ ||

English translation:

We would be offenseless (áditi) sons of Aditi, and a fortress among gods and mortals, o Vasus.
Winning (this) we would win, o Mitra and Varuṇa. Becoming (this) we would become greater, o Heaven and Earth.

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Another Rik says Aśvins are Vasus, Rudras

Rig Veda 1.158.1 - Dedicated to Aśvins

वसू रुद्रा पुरुमन्तू वृधन्ता दशस्यतं नो वृषणावभिष्टौ । दस्रा ह यद्रेक्ण औचथ्यो वां प्र यत्सस्राथे अकवाभिरूती ॥
vasū rudrā purumantū vṛdhantā daśasyataṃ no vṛṣaṇāv abhiṣṭau | dasrā ha yad rekṇa aucathyo vām pra yat sasrāthe akavābhir ūtī ||

English translation:

You two Vasus, Rudras, who give many counsels, strengthening (our praise) in preeminence—favor us, o bulls, since the son of Ucathya [=Dīrghatamas] is the legacy (left) for you, wondrous ones, since you two have run forth (to him) with unstinting help.