1 Year Planning and Scrum Short Term - How to approach

If it was actually possible to have a "clear 1 year roadmap", why would the organization need Scrum at all? Scrum is about innovation under complex conditions of high uncertainty, and learning to build the right thing at the right time.

Frameworks such as Scrum are designed for use in a complex environment. In such an environment, it may not be possible to have a reliable roadmap that is more than a few weeks or months long. Any effort put in creating, communicating, and revising such a roadmap would be wasteful and would only take away time from valuable work, like developing the product.

For environments that can create long-term roadmaps that are reliable and hold true, then perhaps agile and adaptive frameworks like Scrum introduce more waste by having more frequent planning sessions. If you can sit down for a few days and plan 4, 6, or even 12 months out, you'd spend less time planning than you do in Scrum. However, there are few organizations that have such long-term clarity.

clear 1 Year Roadmap

It would help if you defined what "clear" means. Clarity is not bad if we understand where the limits are and realize that plans are plans and things may not necessarily go according to the plan.

Like in real life, it is good to have a plan to define your goals and provide direction but we know nothing is certain in life. The more important is the ability to adjust and even change the goals if that makes more sense. 

Define the Product goal, and define the chain of interim strategic Goals leading towards this Product Goal.

If the Goals are granular enough those might become your Sprint Goals. Or you might need another layer between the Product Goal and the sprint goals. 

The Sprint Goals must answer "Why is the Sprint Valuable". How does it get you close to the Product Goal? Or maybe reduce the risk of failure? Or provide better clarity if the Product Goal is actually realistic? Or let the stakeholder capitalize monetary value earlier etc...  Think of how to measure that value, so it is not illusive. 

Keep in mind that those interim Strategic goals are subject to change as you learn more Sprint by Sprint. 

I think both sides need to make some consessions. Agreed, scrum is meant for situations were there is an uncertainty. That's one of the main reasons to use it. So the organisation should try to understand that the power of the team lies in the agility (adaptation) and therefore needs to have some uncertainty to be able to be succesful.

On the other hand: my organisation also requires to get a better understanding of what's in store, in order to assign budgets or align with innovation and production in other departments. 

I once did a simple retrospective with the team that pitched them in a fictional 'battle' with their one-year-ahead counterparts, that had travelled back in time to compete with our current product. I may sound childish, but it enabled the team to think free and 'dream' what would have changed in a year. How was 'their' product better than ours? It helped to set some major targets to work on.