Someone gave me some Roselle seeds. I live in Buffalo and I know this is a tropical plant. Is it a plant that can do well indoors?
You certainly can start the seeds indoors and move the plant outdoors after danger of frost.
This plant would not do well in an indoor location and wintering over indoors is also not possible.
You can collect seeds again in the fall and start the process over again.
https://www.gardeningknowhow.com/ornamental/flowers/roselle/growing-roselle-plants.htm
I would like to know information on growing rosa de Jamaica, how big does it get? What type of sun or shade does it like? It's a tropical plant, I believe, that flowers and can be used to flavor drinks, etc.
This article will give you more information on the subject: https://www.gardeningknowhow.com/ornamental/flowers/roselle/growing-roselle-plants.htm
My Rosella plants are flowering, opening and closing for a few days now, but suddenly in the morning I see the flowers are on the ground. The plant is a couple of metres high and looks healthy, no drooping leaves and plenty of buds. Any thoughts please?
Make sure it is getting plenty of sun. Also check for insects that favor buds such as thrips, mites, or lace bugs. Bud blast can occur with environmental problems like temperature extremes or improper watering. These articles should help:
https://gardeningsolutions.ifas.ufl.edu/plants/edibles/vegetables/roselle.html
https://www.gardeningknowhow.com/plant-problems/environmental/bud-blast-in-flowers.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/controlling-thrips.htm