After consulting various Arabic and Urdu dictionaries, we did not find the word Ruhab (روحاب) or Rohab (روہاب) with a waw. However, Arabic dictionaries do contain the words رُحَاب and رُهَاب without a waw.
رُحَاب (with a damma on ر, a fatha on ح, and a sukoon on ب) means "spacious and vast". It is therefore correct to use this name, without a waw. رُهَاب (with a damma on ر, a fatha on ه, and a sukoon on ب), however, means "an inner illness", and it is not correct to use this as a name.
Instead, a name should be chosen from those of the Azwaj Mutahharat or other Sahabiyat, may Allah be pleased with them all, or any other name with a good meaning.
Allah the Almighty knows best.
Darul Ifta Al-Ikhlas, Karachi.
القاموس الوحید: (ص: 606، ط: ادارہ اسلامیات)
الرُّحاب: کشادہ، بڑا
و فيه أيضا: (ص: 675، ط: ادارہ اسلامیات)
الرُّهاب: طبِ باطنی میں اس بیماری کے خوف کو کہتے ہیں جو چار دیواریوں کے درمیان گھرے ہوئے علیحدہ مکان یا جگہ میں پائی جائے۔