Ok you have lost me a little because the HoBao Hyper 7 is kinda brand new and only been offered by HPI since December of last year.
Since this is your first post we will need a little more information.
The Roto Start systems use a battery pack and if it is not fully charged it will not turn the motor over that turns the engine over.
The Nitro engine could have become flooded with fuel since you are new to nitro engines this is not uncommon for you to flood the engine when attempting to start it. Clean around the plug with a blast of nitro cleaner then pull the glow plug then stuff a piece of paper towel down into the head. Turn the engine over until it is clear of fuel.
Did you charge the Roto Starter Battery pack up? If not it will need charging.
If you charged your battery pack then it is something else like the roto start system installed on to your nitro engine.
The one way bearing is the key to starting a nitro engine and might be slipping.
But I more think that is a battery charging problem on the Roto Start.
The Hobao Hyper 7 is one of the longest running unchanged models in RC. Still available brand new, it has been hanging around virtually unchanged for around 10 years. I haven't even seen the HPI model which you refer to (totally disgusted with HPI the last year or so, this is part of the reason why), I'm talking about the Hobao original sold under the OFNA brand in the US, and now under HPI.
The Hyper 7 spawned a whole range of 1/8th buggies, and despite never discontinuing the base model, many new generations were produced, including the 7.5, 8, 8.5, 9, 9.5 and the Star. Always primarily a racing vehicle in more expensive kit form, RTRs were also produced with lower spec components of many of the range of models.
HPI recently acquired the distribution rights for Hobao from OFNA, who replaced Hobao with another OEM which I can't remember at the moment. From that moment, the Hyper side of things has gone awfully quiet, and I just hope HPI get their act together with the new Hobao products soon. Hobao assumedly continues to distribute their own products in Europe (I hope, I need to study the relationship with HPI closer), and Hong Nor remains under OFNA in the US.