The fuse time should tell how far this bomb can roll so as to explode and stop the bomb from rolling once the fuse time has finish lighting up.

that is a very fast rolling speed, which means it could go pretty far. hmm, i am okay with it, but the blast area should not be bigger then a 4 star deconstructor bomb at 5 star sense it has this unique mechanic. Also why not make it deal a status, so as to reduce the damage.

Change knockback of Nitronome to KnockDOWN of DBB and I'm all in...

It sounds like a gun rather than a bomb..

it will bounce off to another direction if it touches an enemy or a wall
Dunno if you added this up there from before, but in my own head it plowed through enemies like a magnus charge (not dealing damage, just pushing them) before exploding after a certain distance. If that were the case it could simply explode upon hitting a wall.

But I can see how the bouncing can work. Feels more bowling-esk to "knock the pins down" rather than having the bomb bounce off the first dust bunny it hits and then just sort of not end up in the crowd you were aiming for.

The Bowling Bomb is, at heart, an Alchemer charge attack
Yeah this is where I disagree with you because alchemers were the first real gun I carried and fell in love with, and the way this bomb is described is nothing like that... Unless you mean the 2* variants but those are rarely a good star level to look at. If anything it more resembles the old callahan charge attack.

I wanted it to have reduced knockback rather than knockdown because that makes it more bomblike IMO. The point of the bomb is to be a bomb you throw into a group of enemies and have it explode from the inside. It's more of a safety bomb than anything else.

Honestly, this sort of bomb opens up potential for various types of 'bowling ball' bombs, such as a bowling vortex, a bowling mist bomb, or a bowling shard bomb. The sort of trade-off I see with this bomb is that, in general, it'll get into groups of enemies and do their thing at a smaller radius. I view it as a sort of "starter" bomb used to chain bombs, or avoid really messy situations.

Granted, I'd prefer just the knockback bomb, as I agree that knockdown is too gun-ish. Not too many guns have an AoE bullet.

Bombs are meant to be short range
When this is the size of a 5* bomb's radius, I find it hard to believe they are "short ranged".

Bombs are an area of effect (AoE) weapon. A bowling ball bomb would be like a 3* bomb dealing 5* damage without taking the steps to become crowded by enemies. Bowling ball bombs would give up the size of the explosion for allowing a safer distance from their targets, which means you'll be doing less damage to crowds of enemies because you aren't reaching all of them, however you'll be doing damage without being at an immediate risk.
As of right now, bombers are a very risky play style. Both other classes have "safe" weapons (brandishes, blasters... Well really any gun), but bombs do not. Adding a sort of "safe" weapon would be good.

Also remember that a bowling ball bomb does not replace other similar bombs, as they must be rolled. If enemies get right up next to you, you'll have problems.