Still seems very elaborate
Level 3
You provide three features. Published Bard subclasses tend to have only two, College of Swords has 3, so high end but OK.
Thasha's Hideous Laughter (THL): Adding a known spell is not listed directly, but it seems this is no stronger than adding a spell and slot 1/day, which is worth 2 points on detect balance. The scaling for higher levels increases the utility without making it overpowered.
No heckling: A added cantrip is worth 2 points on detect balance.
Being able to cast it as a Bonus Action conditional on a miss: increases the overall damage output, with a typcialtypical 35% miss chance, and 60% fail chance on saves, adds 0.5-2 expected damage per attack. Attacks are very common, and Detect Balance scores Advantage on common rolls with 8 points. Here you impose Disadvantage after about 20% of your attacks. This would be worth about 2 points intitallyinitially, and with multiple affected attacks, a multiple of that later.
Roast: maybe comparable to cutting words, with more duration and less in-combat application.
It seems power level here is roughly in line with a Lore Bard who gets 3 Skills, worth 8 points, and Cutting Words. I'm not sure about the disadvantage which feels quite strong, you should test it.
Level 6
You again provide 3 features. Nearly all published colleges have just one, College of Creation two. Many are very simple and short. Lore has one short paragraph, Valor has 2 lines of text. 3 is too many, I think. Elegance in design comes from simplicity.
Maybe the issue is that you are trying to overload Tasha's Hideous Laughter, to a point where the effect has not much in common with the simple first level spell it once was, with areas of effect, dropping concentration, extra range, psychic damage, etc. pp. I also think dropping concentration on an effect that possibly removes multiple opponents from combat is very dangerous.
Maybe do something simpler, like "You are Killing it" as a reskinned Hypnotic Pattern domain spell that has targets bend over in painful laughter and deals a bit psychic to soften them up?
Level 14
A reskinning of an existing level 14 college effect by definition should be balanced, if there are no broken interactions with other features. And this does fit the theme nicely.
I don't know if you have the stomach or interest to go through a 4th iteration, or just try yours as is and see how it goes. Have fun.