[name_f]Sylvie[/name_f] [name_f]Rose[/name_f] is stunning. Look no further
I’m not a great lover of [name_f]Rose[/name_f] as a middle name, its very filler ish, but [name_f]Sylvie[/name_f] [name_f]Rose[/name_f] has to be an exception, because its beautiful.
In general, I’d agree it’s too often used as a filler, but [name_f]Sylvie[/name_f] is SO hard to find middles for and this is a nice combo. I think I prefer Sylvie Iris
Maybe [name_f]Sylvie[/name_f] [name_f]Rosa[/name_f] could keep the sounds but make it a bit more distinctive?
([name_f]Sylvie[/name_f] [name_u]Wren[/name_u] or [name_f]Sylvie[/name_f] [name_f]Ardith[/name_f] or [name_f]Sylvie[/name_f] [name_f]Lark[/name_f] or [name_f]Sylvie[/name_f] [name_f]Lilac[/name_f]?)
[name_f]Sylvie[/name_f] [name_f]Rosalind[/name_f] would be lovely! Or [name_f]Sylvie[/name_f] [name_f]Rosamund[/name_f], for a bit of extra strength and gravitas with such a sweet, pretty first name.
[name_f]Sylvie[/name_f] [name_f]Iris[/name_f] is very nice and my favourite of your options. [name_f]Belle[/name_f] is far too sweet for [name_f]Sylvie[/name_f] [name_f]IMO[/name_f], and [name_f]Rose[/name_f]… It’s undeniably a lovely, classic name but I’m afraid I find it too overused as a middle to get excited about. It does flow well but it flows well with almost everything and therefore seems to be every other little girl’s middle around here. Looking at your boys’ fabulous names, I think you can come up with something more striking!
[name_f]Sylvie[/name_f] [name_u]Rue[/name_u] may appeal to you as a quirkier alternative to [name_f]Rose[/name_f]?
Aw, it’s a shame your husband doesn’t love the longer ros-names.
I do absolutely adore rose in the first name spot but find that when adding a last name to [name_f]SYlvie[/name_f] [name_f]Rose[/name_f] (or really any other first name), [name_f]Rose[/name_f] tends to get lost in there as it’s a pattern one has heard so often, it doesn’t stand out to me anymore.
I find [name_f]Rose[/name_f] a beautiful, classic name- perfect for a middle name!
[name_f]Sylvie[/name_f] [name_f]Rose[/name_f] is absolutely gorgeous!! I dont think it’s plain at all.
Oh my, [name_f]Sylvie[/name_f] [name_u]Rue[/name_u] is gorgeous!! I will have to bring this up to him 
I don’t think it’s plain at all! [name_f]Sylvie[/name_f] is spunky and fresh, and [name_f]Rose[/name_f] is classically beautiful. The imagery is also lovely - [name_f]Sylvie[/name_f] is rooted in the Latin word for forest, so I see a wild rose bramble growing in a secluded woodland glade, deep red blossoms under dappled sunlight.
[name_f]Sylvie[/name_f] [name_u]Rue[/name_u] is also a fantastic suggestion!
[name_f]Rhodeia[/name_f] is my favorite “rose” name… But [name_f]Sylvie[/name_f] [name_f]Rhodeia[/name_f] doesn’t speak to me like [name_f]Sylvie[/name_f] [name_f]Rose[/name_f] or [name_f]Sylvie[/name_f] [name_u]Rue[/name_u].
[name_f]Sylvie[/name_f] [name_f]Rose[/name_f] is beautiful! I don’t think it’s “too plain” in this instance as [name_f]Sylvie[/name_f] isn’t wildly popular.
My middle name is [name_f]Marie[/name_f]. I graduated with more girls with the middle name [name_f]Marie[/name_f] than girls with a different middle name. It never bothered me. BUT I’m named after my aunt so I loved it for it’s significance. The fact that [name_f]Marie[/name_f] was common may have bugged me if there was no reasoning behind it.
I’m giving my son the middle name [name_u]James[/name_u] after my dad. It’s the most common boy middle name I believe, but I’m glad I’m honoring my dad and I expect my son will like having his grandpa’s name as part of his own.
If it was just for the sake of flow, with no meaning, I would try to pick something more uncommon and unexpected.
I think [name_f]Sylvie[/name_f] [name_f]Rose[/name_f] is gorgeous. [name_f]Sylvie[/name_f] is quite spunky and it has some gumption. And [name_f]Rose[/name_f] is sweet and beautiful. They balance each other well. I also love [name_f]Sylvie[/name_f] [name_u]Rue[/name_u]. I plan on going with [name_f]Sylvie[/name_f] [name_u]Blue[/name_u] for my first baby, if I have a girl… and if I can convince my partner. If you like that, feel free to use it, yourself, if you and your partner like it. Good luck!
I would personally avoid it, I feel as though every little girl has [name_f]Rose[/name_f] in the middle these days and it can lack creativity.
However, [name_f]Sylvie[/name_f] [name_f]Rose[/name_f] is gorgeous, and [name_f]Rose[/name_f] does make pretty much every name sound beautiful, so you should stlil use it if you love it!