Yes.

The amount needed to fill that gap will look terrible and will separate anyway from heat/cooling cycles.

In case you want a 2nd opinion, ditto Handymac.

Not saying silicone won't work, short term.
But short term it is.

Before you re-insulate your attic, you will mitigate lots of your icicles and damming issues if you air seal the attic first.

Warm air enters the attic from multiple sources within the house. this warms the roof deck which melts snow. The remaining snow acts as an insulator, so if you have lots of snow you don't notice the hot spots from outside and the roof looks to be uniformly covered with snow.

But that water runs down your roof, as it is supposed to, only to find a much colder area where your roof projects (the overhang). There is freezes and builds up, pushing the downward running water back up the roof. doesn't matter if its a gush of water or just a small trickle.

By air sealing your ceiling to attic area and insulating well after and having good air flow in the attic (soffit and ridge venting) you eliminate much of the problem of water/ice dams.

"By air sealing your ceiling to attic area and insulating well after and having good air flow in the attic (soffit and ridge venting) you eliminate much of the problem of water/ice dams."

It depends entirely on local weather.
If the melting is being frozen by sunlight on the snow while the air temperature remains below freezing the melt runoff freezes at the overhang where the roof has air on both sides.

If the heat is coming from leakage sealing can help reduce it, but it often is not a complete cure in areas near the rain/snow line for winter weather.

Ya, that why I said "much" of the problem.

I've always increased the size and slope of my eavestroughs to facilitate the ability of that near frozen water to get gone as well. Aggressive slope cures lots and you can trim it or paint it to minimize the street look.

We have a few homes in Calgary and it can Chinook on you, be well above freezing and then drop, leading to immense ice issues if you don't get out in front of them. Between air sealing, insulation and good drip edges along with attention to the troughs and downspouts (don't make freezing water travel too far before you divert it down) we have substantially minimized our issues.

And Brick is right, each home is a bit different, each geographical location is a bit different and here in Canada we don't have stuff like air handlers, hot water tanks or aircon in our attics, so you have to watch for those variables as well.

"Aggressive slope cures lots and you can trim it or paint it to minimize the street look. "

And that is why houses in snow areas tend to have steeper roofs.

It is the houses that are not built to match their location that often have more significant problems.

Like putting exterior tile work in freezing areas, low sloped roofs in snow areas, etc.

The insulation will be part of a hot roof system--sealed attic, no ventilation. There is HVAC up there.

In addition I want to heat the gutters at least. Heating wires are cheap to install but I'm not sure how well they'll work. I'm looking at the heated roof edge panels, but can't find any local dealers in MA.

But the first issue is coughing up 4K to pull down the ice and water shield. The original roofer is the one that wants to do the silicone bead, even though he admits the shield doesn't overlap the fascia.

"The insulation will be part of a hot roof system--sealed attic, no ventilation. There is HVAC up there."

Question. Do you have HVAC ducting in the rafter bay(s)?

Not in the bays. It's a new high efficiency system with insulated ducts running along the floor. The layout/construction etc. of the house made it extremely expensive and impractical to run up from the basement, which was the original idea, so up in the attic the systems went. The system itself does not appear to radiate much heat or moisture into the space, if any.

Also, the house has very wide eaves, a hip roof, and a sunny location. That means snow will melt no matter how good the insulation is, to some extent. It will freeze over the eaves, because they project quite far from the house. And effective venting isn't very easy, because of the hip and short ridge. So I think I need multiple levels of defense against ice dams.

That info changes a lot. Well beyond my area of knowledge now.

I used to live beside an old guy (sort of like i am now!) who filled pantyhose with salt and laid that out (doing the splits) along the roof edges, just above the gutters.

His theory was the water came down, nibbled at the salt and therefor raised the freezing level. I'll leave it to you to decide how to collect enough pantyhose to accomplish such a thing, assuming his idea makes any sense at all.

We have 30" eaves and solved all our problems by removing the gutters. No leaves to clog or clean out. No excessive ice on the edge of the roof and no more leaks in the basement where the gutters overflowed and dumped all the water in one spot.

With the proper landscaping we can now have a 10" rain without water in the basement.

Hendricus, glad you've solved your problem.

That won't be the solution everywhere though.

This sums it up:

"If the melting is being frozen by sunlight on the snow while the air temperature remains below freezing the melt runoff freezes at the overhang where the roof has air on both sides."