There are a great many Buddhist rituals which vary across Buddhist schools and traditions. Did the Buddha describe any rituals which were to be done as part of practice in the Pali canon? Or are the rituals we see today later additions perhaps emerging from specific cultural or historic contexts.
I do not know of a sutta where the Buddha suggested ritual. (There may be one; I just don't know of it.) But I do know of a sutta where the Buddha guided a follower to understand that ritual is ineffective. In SN 42.6, Paccha-bhumika Sutta: [Brahmans] of the Western Land the Buddha gave 4 examples of crowds trying to affect an outcome with rituals. Here are two for example:
"Very well, then, headman, I will question you on this matter. Answer as you see fit. What do you think: There is the case where a man is one who takes life, steals, indulges in illicit sex; is a liar, one who speaks divisive speech, harsh speech, & idle chatter; is greedy, bears thoughts of ill-will, & holds to wrong views. Then a great crowd of people, gathering & congregating, would pray, praise, & circumambulate with their hands palm-to-palm over the heart [saying,] 'May this man, at the break-up of the body, after death, reappear in a good destination, the heavenly world!' What do you think: would that man — because of the prayers, praise, & circumambulation of that great crowd of people — at the break-up of the body, after death, reappear in a good destination, the heavenly world?"
"Suppose a man were to throw a jar of ghee or a jar of oil into a deep lake of water, where it would break. There the shards & jar-fragments would go down, while the ghee or oil would come up. Then a great crowd of people, gathering & congregating, would pray, praise, & circumambulate with their hands palm-to-palm over the heart [saying,] 'Sink, O ghee/oil! Submerge, O ghee/oil! Go down, O ghee/oil!' What do you think: would that ghee/oil, because of the prayers, praise, & circumambulation of that great crowd of people sink, submerge, or go down?"
The sutta ends with the only effective "ritual" that I'm aware of from this time; which is the listener going for refuge.
"I go to the Blessed One for refuge, to the Dhamma, & to the community of monks. May the Blessed One remember me as a lay follower who has gone for refuge from this day forward, for life."
Most of the Buddhist rituals are about paying respect to the Triple Gem. Paying respect is praised and encouraged in the Suttas.
Asevanā ca bālānaṃ paṇḍitānañca sevanā, Pūjā ca pūjanīyānaṃ etaṃ maṅgalamuttamaṃ. - Not to associate with the foolish, but to associate with the wise, and to honor those worthy of honor — this is the highest blessing - Mangala Sutta
"Here, student, some woman or man is obdurate and haughty; he does not pay homage to whom he should pay homage, or rise up for whom he should rise up, or give a seat to whom he should give a seat, or make way for whom he should make way, or worship him who should be worshipped, or respect him who should be respected, or revere him who should be revered, or honor him who should be honored. Due to having performed and completed such kammas, on the dissolution of the body, after death, he reappears in a state of deprivation... - Cula-kammavibhanga Sutta