The gemara says in Beitza and Bava Basra that the measure of person's mezonos is determined on Rosh Hashana. What is a wonder is why this statement appears nowhere in the most obvious place - Maseches Rosh Hashana!
The gemara in Taanis [2a] says in the name of Rav Yochanan that geshamim and parnasa are the same thing and have the same Divine "key". That is quite a surprising assertion being that on Rosh Hashana parnassa is decided and only later on Succos, rainfall is decided. This indicates that they are two separate things. He argues with the Bnei Ma'arava who hold that geshamim and parnasa are two different things. We follow the opinion of Rav Yochanan.
The gemara in Beitza [16] says as follows: The entire sustenance of man [for the year] is fixed for him from New Year's [Festival] to the Day of Atonement, except the expenditure for Sabbaths and the expenditure for Festivals and the expenditure for the instruction of his children in the Law; if he [spent] less [for any of these] he is given less and if he [spent] more he is given more. Said R. Abbahu: What verse of Scripture [supports this]? ‘Blow the horn at the new moon at the בכסה for our feast-day’. Which is the Festival on which the moon is concealed? Say, it is New Year; and it is written [with respect to this Festival]: ‘For it is a statute [chok] for Israel, an ordinance of the God of Jacob’. How is it implied that the word chok connotes sustenance? For it is written: ‘And did eat their portion [chukkam] which Pharaoh gave them’.
Why does the gemara expound "Which is the festival where the moon is concealed". Say more simply - "Which is the festival where we blow the shofar - Rosh Hashana" [as it says תקעו בחודש שופר].
It would seem then the the gemara is understanding the pasuk very simply. תקעו בחודש שופר - On Rosh Hashana, בכסה ליום חגינו - Referring to Succos when we sit covered by the succah and כסה is the same letters as succah, כי חק לישראל הוא - On Succos Hashem determines our mezonos, משפט לאלקי יעקב - There is a judgement on life on Rosh Hashana. [This style of the earlier and latter part of the pasuk being thematically interrupted in the middle as it is here is quite common in tehillim]. Meaning that the shofar effects a positive judgement for life and the Succah for water.
Meaning that according to the simple understanding of the passuk, on Succos we are judged both for mezonos and water. The chiddush of the gemara's drasha is that "Chok" is a reference to Rosh Hashana and it is then that Hashem judges us on our mezonos and life.
According to this we can say that the sugyos in Beitza and Bava Basra follow the Bnei Maarava who contend that geshamim and parnasa are two different categories. If so we can say that there are two different judgements - parnasa on Rosh Hashana and rain on Succos. However according to Rav Yochanan [and the way we pasken], both mezonos and rain are decided on Succos [as per the simple understanding of the pasuk]. That is why the gemara in Rosh Hashana never cites the statement that a person's mezonos are determined on Rosh Hashana.
It emerges then that we have a CHIDDUSH NORA on our hands. According to the עיקרי הסוגיות in Rosh Hashana the judgement is not from Rosh Hashana to Rosh Hashana but from Succos to Succos!
But no rishon or acharon says this so we will not inscribe it in stone:-).
עפ"י הספר מרבה טובה עמ"ס ביצה עמ' רלח-רלט
מאת מו"ר הרה"ג ר' יעקב דוד המניק שליט""א