We are not only missing certain sources of candy, but we're also straight up missing candy from places that should drop them right now.
We only have Megaton Parfaits available from the NPC shops right now. This could be improved a lot as it has been on JP -- many weapon badge shops had various candies over the years.
The CF situation seems to be going well at the very least with Stat-Stamina cookies being in the 13* egg collections. These cookies are super important to summoner and were painful to get in JP, so this is an improvement. Only just recently did they start handing them out again. (for reference -- I paid 5m per cookie just to get 12 of them and there were only like 20 on the market at the time -- they're down to at most 1m each now)
Rolls: Currently the most important rolls that need to be addressed are Steadfast Roll, Conversion Roll, and Bravado Roll (NA name pending for the last 2).
Steadfast Roll (JP name: ふんばりロール) - Only source is titles. In JP, this is a possible Recommended Quest reward from the box, as well as just straight up available from the shop for weapons badges. More sources of these are very nice, this is a very good roll
Conversion Roll (NA name pending, JP name is へんかんロール) -- Unavailable. Should be dropping in Naverius Ultimate, also available to buy in the same place you buy Nemesis weapons on JP. This roll is quite important for SuFi in EP5 as it makes Melon very, very good before Su swaps to full TEC build in EP6. Melon also falls off in EP6 due to enemies having high damage, causing it to die from Dia Master very easily.
Substitution Roll (JP name: みがわりロール) -- Only source is currently Titles. Should be dropping in Lillipa Ultimate. Same as above with Raven weapons too.
Bravado Roll (NA name pending, JP name is つよがりロール) -- Unavailable. Only available with weapon badges and certain collection files, does not drop anywhere in JP. This Roll first debuted with a Collection File for Ultimate Amduskia in 2016-2017. It was readded into a Collection File from July 2018 to January 2019 that was meant to be completed with the Urgent Quest that Global just got in early November, Dying of Depths. Lastly it became a part of the permanent 13* pet collection file as an additional reward for some pets. This roll is INSANELY important for many bossing situations, as pets have very low defense compared to players generally.
Sympathy Roll (NA name pending, JP name is いたわりロール) -- Unavailable. Frustratingly rare in JP as well, unfortunately -- until the recent Urgent Quest added there revived it. Has niche uses, but generally isn't used much in current JP content. Only content that gave it was the Christmas 2018 seasonal.
Fluffy Roll (NA name pending, JP name is ふんわりロール) -- Unavailable. Honestly a pretty unused roll anyways, but only was available from a collection file 1 year ago for a seasonal. This is arguably the lowest priority of the rolls to worry about, since Crisis Roll pretty much does the same thing and is extremely accessible thanks to the shop. It's also technically an Episode 6 roll, and is the last roll they've made in recent times.
Barrier Roll (NA name pending, JP name is いたわりロール) -- Unavailable. Core roll for certain content that will appear in EP5 if you want to do an extremely excessive challenge. Only came from Collection Folders in JP, though. Outside of that one very specific challenge, this roll is fairly unused.
Parfaits seem to be somewhat being addressed but rolls just seem forgotten in all of this -- Support Rolls are the most popular and very, very good, but they drop and so we have sources of that and its not an issue... at least at the moment. People use way more than Support Rolls. It's part of the reason Summoner is such an in-depth class because there's no "best box" for any pet at all given points in time. People will do their boxes differently and very often end up with different results, especially because again, pets have below average defense and rolls are a way to help deal with that.
EDIT: Support Roll should be set due to Yamato triggers being buyable in the badge shop now. This actually solved a separate issue of Yamato Factor availability that I saw to be an issue on the JP side, so I'm very happy about this.
One thing you may notice is a lot of the word "seasonal" in this. Yeah, a lot of candy was seasonal specific. This includes parfaits, and even cookies -- but the most recent cookies that were added were extremely recent and so don't necessarily need to be addressed right away (Stat-Spiritas). Stat-Stamina Cookies have already been addressed in this, and Parfaits slightly addressed with Luxury and Vigorous Parfaits being in the mission rewards, but there's still tons to go. Rolls are just the gigantic elephant in the room, particularly because there hasn't been a new Roll for pets in ages on JP -- it's just the Parfaits that are improving, really (outside of Invincible roll getting a stealth buff at some point)
The other thing you might notice beside "seasonal" is "Collection File." I think this is even more of a reason that candy is missing because quite a few candies only had their actual source be the Collection File. This is primarily rolls, but there's a couple Parfaits that were missed too -- some notables being Super Vigilant Parfait (超みまもりパフェ) and Spirited Parfait (はりきりパフェ).
Conversion rolls are definitely the most important thing in my eyes that need to be added. I'd like to experience EP5 Melon on SuFi before we swap off of the MEL side of summoner in EP6. And on top of this, it's literally the only thing missing in Ultimate Naverius at this point -- we even have Dia, Ares, and even Novel weapons dropping there now. So why are the rolls missing?
I should note that JP made a lot more candy available through a collection file that's available 24/7 as well, but we have stat-stamina cookies so I dunno that I can really complain other than that they get 6 different candies per CF done (and not all of the CFs are the same!) whereas we get 3. The plus side is that stat-sta's are super, super cheap and easy to get on Global which is a massive plus though.