Help with sign?

I would be really grateful if someone could help me out. I'd like to make a door sign for someone called 'Rowan' - ideally will have Pedo Mellon a Minno along the top and the translation for 'This is Rowan's room' on the bottom (might be better to translate 'This is the room of Rowan'. I'm having trouble figuring out how to denote possession. Would that end up being Hen Sam Bregalad? Sin Sam Bregalad? Hen/Sin Sam-en-Bregalad? I think I prefer Bregalad to Faran as a translation for Rowan.

As I always say, dictionaries alone cannot help with grammar, especially when dealing with complex languages like Sindarin.

As the initial part of the Moria Inscription (i.e. the "mellon phrase") shows, possession is denoted by having two nouns follow each other (directly and without mutation) like: Ennyn Durin "Doors (of) Durin", Aran Moria "King (of) Moria". The word en is "definite", so using it before a name would be like saying "The Jessica". Continuing, sen (or lenited hen) is the accusative and adjectival form of "this", while this phrase needs it in nomative form, and that would be si (or se by reformation). Then there is "sam" which should rather be tham, because the form sammath is simply the result of dissimilation (cf. úthaeth > úthaes) due to having two "th" sounds in the same short word. Finally, Bregalad does not mean "rowan", because it is simply inspired by the Old English word for rowans "cwic-beám" (i.e. "quick-tree"), and the Sindarin name is a calque of that, belonging an Ent who happens to concern himself with rowans (while the name only refers to his hastiness, unrelated to rowans).

As for faran, it may not be the best choice. Its root is √PHAR(AN), which does not work as an extension of ᴹ√PHAR (which yields words like "enough, sufficient; sate, suffice" and is thus important to keep), while the alternative ᴹ√PHER(EN) seems to refer to beeches instead (though arguably they are similar to rowans). In any case, one should not use a common noun as an Elvish name, as Elves formed names by adding at least a masculine/feminine suffix, if not by compounding another word. So I will offer Farandir & Ferendir "Rowan/Beech-man" and Farandis & Ferendis "Rowan/Beech-woman", the choice is yours.

And the phrase:

Si tham [Name]

Thank you so much! This is why I thought it would be best to ask because all languages have their pecularities with grammar and style and didn't want to get it wrong.

I was wondering if I could get some further help. I have been asked to add in the phrase 'Always remember the road that leads you home'. I have been doing my best to research what I can - not sure about getting 'always' but I have ended up with [Ui] reno men han tûgdhir bar? Not sure if bar should be mbar (haven't quite got the hang of mutations) and have no idea if I've done the right conjugations with the verbs. However, I feel like there isn't any point in asking for help if I don't at least try and make a stab at it myself!

Also, out of interest, I was lobbying for 'Here there be dragons' but it has been vetoed - I have attempted to translate that as Sí sêv emlyg - did I get close?

Not sure how you ended up with "tûgdhir", I would recommend staying away from whichever "source" led you to it, as it manages to include about five mistakes in such a short word. I appreciate your effort, but I would rather receive simple requests than fix mistaken attempts. I am happy to help with the latter as well, but only if it will serve one's studies (which is rarely the case, so I often end up writing long explanations for nothing). Thus, unless you are dedicated to learn Sindarin, I would suggest simply asking for translations in the future. Here:

Uireno i-ven i dôg gin na mar.

As for the "dragon" one, I don't recognise "sêv", but I would assume that you were trying to conjugate sav- "to have", thus translating "here(this place) has dragons". But you applied I-affection (turning A into E, which only happens if there is/was a following I) to it, probably due to forms like sevin "I have" where there is an I to cause the vowel mutation. The 3rd p. sg. form of sav- is simply sâf (and it's "-f" because Tolkien spelled Vs at the end of words as F, so final F is read V).

Also since you mentioned a "sign", you probably want to have these transcribed with Tengwar. I recommend using Tecendil for that. Be sure to pick the appropriate Tengwar Mode and the font of your choosing.

Thank you so much again!