Rolls-Royce (LSE:RR.) shares have delivered disappointing returns over the past eight months. While other growth stocks such as Nvidia, AMDAND Alphabet increased by more than 20%, the engine manufacturer’s inventories are essentially flat.

So, what’s going on here? And are shares still worth considering for an ISA or SIPP?

The environment has changed

The reason why stocks are underperforming is quite elementary. The operating environment has changed…drastically.

Although Rolls-Royce is a diversified company today, it still generates a enormous part of its revenues from servicing aircraft engines (these are counted in flight hours). And with high oil prices caused by conflict in the Middle East, global airlines are cutting back on flights, which means there is uncertainty about flight times.

This change in background is likely to worsen Rolls-Royce’s performance in the near term. I don’t think the 2026 results will be disastrous (the group said the background change is manageable), but they most likely won’t be as good as they could be if crude oil continues to trade at $60-$70 per barrel as it was at the start of the year.

For example, the company’s first-half results may indicate that the group may not raise its earnings forecasts, as has happened repeatedly in recent years. Performance could be more in line with expectations (or perhaps slightly worse).

Breathing break

It could also be argued that this was intended to be a period of share price consolidation. After all, from the beginning of 2023 to the end of 2025, the stock increased by more than 1,000%.

No stock grows in a straight line forever. At some point there is always a period of consolidation during which past gains are digested and fundamentals catch up with valuations (note that valuations in this case remain quite high).

This is no longer a game of momentum

Another factor may be a breakdown in dynamics. Currently, there are many funds (and investors) that track the dynamics of share prices and invest in shares with high dynamics (which gives these shares an additional impetus).

Given that the upward trend in share prices has recently broken down, these shares are now less attractive from the point of view of lively investing. This may result in poorer results.

Is it worth visiting today?

Is it worth taking part in shares today? Well, they could be – there’s certainly less hype around them and I consider that a good thing.

That said, I think it’s worth the wait. I remain confident that we can expect better shopping opportunities in the coming months.

My personal feeling is that the stock will fall back to around 1,000p. This hunch is based on a combination of fundamental (i.e. changing operating environment) and technical (deteriorating share price momentum) factors.

I think if they dropped back to that level it would be a good opportunity to consider. Because in the long run, this company has high growth potential given its exposure to defense and nuclear energy.

Is it worth investing £5,000 in Rolls-Royce Plc now?

If investing expert Mark Rogers and his team have stock advice, it can pay to listen. After all, Twelfth Magpie’s flagship Share Advisor newsletter, which it has run for almost a decade, provides thousands of paying members with the best share recommendations from across the UK and US markets.

Mark believes there are 6 standout stocks that investors should consider buying right now. Want to see if Rolls-Royce Plc is on the list?

Edward Sheldon holds positions at Nvidia and Alphabet.