Translation:These are not the robots you are looking for.
You can use either. You use "dette" if the robots in question have yet to be mentioned in the conversation.
In any other instance but this.
It can be either if it references something that has yet to be discussed.
No, if anything that's the first thing that comes to mind when a Norwegian uses the word "robot". Less humanoid robots are often seen as "maskiner" (machines), at least by those who don't work in robotics.
I guess a native Norwegian isn't going to give feedback on this sentence. Is it common to use dette to represent 'these' when dette isn't followed by a noun (I can only guess this is the case)?
I'm a native Norwegian and will give feedback. Comments previously provided don't deal with the aspect of Norwegian grammar that is vital to a correct understanding of the use of "Dette". I'll deal with that subject and hopefully will end the existing confusion.
"Det" and "Dette", when used at the beginning of a sentence are used strictly because Norwegian grammar, like English grammar, requires sentences to have subjects. The two words are proxy subjects / proxies for subjects. (In English "it" in the following sentence satisfies the English grammar requirement for a subject. "It is raining." In this instance "it" is a proxy subject and in spite of its appearance, it is not a pronoun -- it doesn't have an antecedent.)
In spite of the fact that "Det" and "Dette" are spelled exactly like neuter articles/ pronouns they do not have gender. Once the words for which they are proxies are known then the subsequently used articles/ pronouns evidence the actual gender of the word with which they are associated.