Long sleeve Roady top

You might find that most long sleeve tops are a bit thicker. Worth considering short sleeves + arm warmers if that’s a problem.

yep, pair of lightweight arm warmers and hey presto, you've got as many long sleeve tops as you have s/s ones!!

As above, arm warmers are the way forward.

You can actually buy sun protection sleeves

Sleeves

I've been looking as I need some as my forearms are becoming more and more sensitive even with sunscreen on.

Ah yes never though of that, good option, thanks.

I have a couple of long sleeve summer weight jerseys and never wear them. As others have said arm warmers are the way forwards.

Stolen Goat do some long sleeve tops (that aren’t Winter/Autumn thickness). I use one quite a bit for gravel rides for a bit of protection from overgrown brambles!

They’re not roady, but Fox do some lightweight , long sleeve tops.

These are really nice. Really lightweight as well.

https://grity.co.uk/collections/cycling-jerseys/products/pritygrity-core-long-sleeve-jersey-men

Yup arm warmers is the answer.

I am still wearing a Rapha core long sleeve but it is too warm to wear much above 15 degrees. Wear it around 9 months or the year (I cycle very early in morning so still cold in June!) and had if for 6 years and it still looks like new. £70 (at the time) very well spent.

How about using sun screen?

I have this one in red which I bought a few years ago. Very lightweight & long sleeves. I think it was pretty much the only option I found when searching 🤔
https://www.highonbikes.com/products/funkier-strike-summer-long-sleeve-jersey-j-730-6l?variant=31757324451936
Love it. I burn like a bastard and sometimes sun cream just doesn’t cut it, if I’m out all day.

I bought a decathlon one very like this for the same reason which while it doesn't scream quality, has actually had loads of use (remember the last two summers?) and has held up fine. Very lightweight and breathable and...... only £20. Don't worry about those brambles!

https://www.decathlon.co.uk/p/men-s-anti-uv-long-sleeved-road-cycling-summer-jersey-rc100-red/_/R-p-307563?mc=8786267&c=RED

Rapha do some good long sleeve tops(sale) 🙌🏻

Rapha do a pair of arm sleeves for the sun, a bit lighter and cooler than normal arm warmers. their pro team long sleeve training jersey is fairly lightweight too.

I've got a DHB one which oddly sometimes makes me feel chillier than some of my short sleeve summer jerseys.

It could be this one - https://www.chainreactioncycles.com/p/dhb-long-sleeve-jersey - but it's a few years old so not sure if identical. Rated as a 'summer' jersey anyway but no stripes I'm afraid.

Ground Effect Rock Lobster

https://www.groundeffect.co.nz/products/rock-lobster-summer-long-sleeve-shirt

Designed to do exactly as you asked.
I have two - they are 12 years old and I'll replace with the same.

Another very happy Rock Lobster user

I have a long sleeve Champion club jersey and it is a favourite of mine - surprisingly hard to source. Otherwise I wear a long sleeve compression top from 2XU underneath - white to reflect the sun. Or just get some white sleeves.

This (randomly?) popped up as a Facebook ad.

https://www.dondacycling.com/collections/jerseys-men

I've no idea about quality etc but I thought the brand name was great. Just go for one 😉

On the roadie side of the spectrum Maap has some ridiculously lightweight long sleeve jerseys.

I tend to wear the evade pro base ls and even when racing in 35degrees it wasn’t too much. the arms are insanely thin, however they do 2 models of lighter weight jersey!?

Very spendy, very “form fitting”. Other colours are available.
https://maap.cc/products/evade-pro-base-ls-jersey-2-0-violet

I recently discovered sun sleeves which could be worth an investigation. I always thought they would be hot like arm warmers or at least clammy, but no they were great!

I'm a huge fan of arm warmers but there's no way I'd use them in summer - much too hot. I didn't realise sun sleeves existed, thanks to all who've mentioned them as they look ideal for running, too.

Lightweight UPF arm warmers, minimal flappage

I have a very thin and breathable long sleeve jersey you can have for the cost of the postage if you’re my size (40”-ish chest). It’s the white and black one (mostly white) second from top in this ad:

https://singletrackworld.com/classifieds/advert/five-jerseys-for-twenty-quid-posted-40-ish/

I've got one of these and I'm impressed with it. Normal jersey thickness, plus the sleeves will push up easily if needs be

https://www.chainreactioncycles.com/p/endura-pro-sl-l-s-jersey-ii?color=fossil

I don't have the summer weight one, but the mid-season version of that Decathlon jersey above, and the winter jacket and they are both great. Extra little pockets on the hip are very helpful and easy to access for snacks/litter.

Torm or sportwool (merino blend)
or Galibier

both excellent

I have one of these
Ground effect Rock Lobster
Cool and keeps the sun off, loose fit. Ground Effect stuff is not so competitive on price for UK customers as it was. Very well made kit though.

SportPursuit have a particularly enticing cycling kit clearance on at the mo'. Rapha and Castelli for much (relative) cheapness.

With apologies to those about to spend money....

I really like my Rapha CX jersey. It's the same as their short sleeve Jersey but, er, longer. They don't seem to do them these days but I guess the 'Core' long sleeve one is similar.

Prendas ones used to be good but as above they're a bit thicker than SS jerseys.