Can the 4 in. x 25 ft. Kwikmesh Utility Screen Roll be flattened out to be siliconed over existing attic vent screens?

Here is some information about flattening the Kwikmesh

Yes it can. After being rolled up from the manufacturing process all the way through distribution to the stores, it will not just roll out flat and stay flat by itself, but with a little effort it will flatten out nicely.