They are required to read you your rights if you're in custody and being interrogated. Roadside detentions are typically not custody (but they may be), so Miranda rights aren't required.

If they were supposed to read you your rights but didn't, the statement and any evidence directly obtained as a result of that statement can be excluded. It doesn't automatically mean the whole case will be thrown out though unless the statement is all they had.

No. You would have an evidence suppression issue only if police or prosecutors seek to introduce as evidence a statement or confession obtained after arrest without advising you of Miranda rights. It would be unusual for police to interrogate after arrest without a Miranda advisement. You might be surprised to find the police reports claim you were so advised.

Of course you can fight the charges. When arrested or charged with any crime, the proper questions are, can any evidence obtained in a test, search or confession be used against you, and can you be convicted, and what can you do? Raise all possible defenses with whatever admissible and credible witnesses, evidence, facts and sympathies are available for legal arguments, for evidence suppression or other motions, or at trial. If you don't know how to represent yourself effectively against an experienced prosecutor intending to convict, then hire an attorney that does, who will try to get a dismissal, diversion program, reduction, or other decent outcome through plea bargain, or take it to trial if appropriate.

Keep in mind a little free advice: When charged or arrested for DUI, whether alcohol or drugs, then upon release from jail or booking the defendant is given documents that include a notice that you have only ten days to file a request with DMV for a hearing on an appeal of an automatic one-year suspension of your license imposed by DMV. That is separate and runs consecutively with any suspension that may be imposed by the court. Contact DMV and do so, timely, then appear at your scheduled DMV appeal hearing and present any supporting evidence and testimony. If you don't know how to do these things effectively, then hire an attorney that does.

If serious about hiring counsel to help in this, and if this is in SoCal courts, feel free to contact me.