L!Ryoma or Laegjarn???

If you already invested into him, you don't really need to try summoning her. She also shares a slot with Laevatein so even if you do decide to roll, it'll be a bit more difficult getting her.

If you care about arena, L!Ryoma is far better than Laegjarn because of his blessing. (he is a very good candidate for the R Flier duel skill though)
If you don't care about arena at all, I would say summon if you like her as a character. They essentially fill the same role with Laegjarn being much tankier. I don't know the exact average amount of orbs Laegjarn takes but I think it's somewhere in the 100s for a specific red unit, this means you could get a Laevatein in pursuit of Laegjarn, or two Laevateins and no Laegjarn. Or even two Laegjarns without a Laevatein. Colour sharing actually provides better odds than a single colour.

Although I would at least wait until the legendary banner or near the end of the Muspell banner to make your final decisions since the banner lasts for nearly a month.